Deploy locks

Add a deploy lock for commands that are unsafe to run concurrently.

The lock is taken by creating a `mrsk_lock` directory on the primary
host. Details of who took the lock are added to a details file in that
directory.

Additional CLI commands have been added to manual release and acquire
the lock and to check its status.

```
Commands:
  mrsk lock acquire -m, --message=MESSAGE  # Acquire the deploy lock
  mrsk lock help [COMMAND]                 # Describe subcommands or one specific subcommand
  mrsk lock release                        # Release the deploy lock
  mrsk lock status                         # Report lock status

Options:
  -v, [--verbose], [--no-verbose]                # Detailed logging
  -q, [--quiet], [--no-quiet]                    # Minimal logging
      [--version=VERSION]                        # Run commands against a specific app version
  -p, [--primary], [--no-primary]                # Run commands only on primary host instead of all
  -h, [--hosts=HOSTS]                            # Run commands on these hosts instead of all (separate by comma)
  -r, [--roles=ROLES]                            # Run commands on these roles instead of all (separate by comma)
  -c, [--config-file=CONFIG_FILE]                # Path to config file
                                                 # Default: config/deploy.yml
  -d, [--destination=DESTINATION]                # Specify destination to be used for config file (staging -> deploy.staging.yml)
  -B, [--skip-broadcast], [--no-skip-broadcast]  # Skip audit broadcasts
```

If we add support for running multiple deployments on a single server
we'll need to extend the locking to lock per deployment.

lib/mrsk/cli/traefik.rb

@@ -1,36 +1,46 @@
 class Mrsk::Cli::Traefik < Mrsk::Cli::Base
   desc "boot", "Boot Traefik on servers"
   def boot
-    on(MRSK.traefik_hosts) { execute *MRSK.traefik.run, raise_on_non_zero_exit: false }
+    with_lock do
+      on(MRSK.traefik_hosts) { execute *MRSK.traefik.run, raise_on_non_zero_exit: false }
+    end
   end
 
   desc "reboot", "Reboot Traefik on servers (stop container, remove container, start new container)"
   def reboot
-    stop
-    remove_container
-    boot
+    with_lock do
+      stop
+      remove_container
+      boot
+    end
   end
 
   desc "start", "Start existing Traefik container on servers"
   def start
-    on(MRSK.traefik_hosts) do
-      execute *MRSK.auditor.record("Started traefik"), verbosity: :debug
-      execute *MRSK.traefik.start, raise_on_non_zero_exit: false
+    with_lock do
+      on(MRSK.traefik_hosts) do
+        execute *MRSK.auditor.record("Started traefik"), verbosity: :debug
+        execute *MRSK.traefik.start, raise_on_non_zero_exit: false
+      end
     end
   end
 
   desc "stop", "Stop existing Traefik container on servers"
   def stop
-    on(MRSK.traefik_hosts) do
-      execute *MRSK.auditor.record("Stopped traefik"), verbosity: :debug
-      execute *MRSK.traefik.stop, raise_on_non_zero_exit: false
+    with_lock do
+      on(MRSK.traefik_hosts) do
+        execute *MRSK.auditor.record("Stopped traefik"), verbosity: :debug
+        execute *MRSK.traefik.stop, raise_on_non_zero_exit: false
+      end
     end
   end
 
   desc "restart", "Restart existing Traefik container on servers"
   def restart
-    stop
-    start
+    with_lock do
+      stop
+      start
+    end
   end
 
   desc "details", "Show details about Traefik container from servers"
@@ -64,24 +74,30 @@ class Mrsk::Cli::Traefik < Mrsk::Cli::Base
 
   desc "remove", "Remove Traefik container and image from servers"
   def remove
-    stop
-    remove_container
-    remove_image
+    with_lock do
+      stop
+      remove_container
+      remove_image
+    end
   end
 
   desc "remove_container", "Remove Traefik container from servers", hide: true
   def remove_container
-    on(MRSK.traefik_hosts) do
-      execute *MRSK.auditor.record("Removed traefik container"), verbosity: :debug
-      execute *MRSK.traefik.remove_container
+    with_lock do
+      on(MRSK.traefik_hosts) do
+        execute *MRSK.auditor.record("Removed traefik container"), verbosity: :debug
+        execute *MRSK.traefik.remove_container
+      end
     end
   end
 
   desc "remove_container", "Remove Traefik image from servers", hide: true
   def remove_image
-    on(MRSK.traefik_hosts) do
-      execute *MRSK.auditor.record("Removed traefik image"), verbosity: :debug
-      execute *MRSK.traefik.remove_image
+    with_lock do
+      on(MRSK.traefik_hosts) do
+        execute *MRSK.auditor.record("Removed traefik image"), verbosity: :debug
+        execute *MRSK.traefik.remove_image
+      end
     end
   end
 end