Print container logs when HealthCheck response_code != 200

The Healthcheck container is shut down right after performing the check, this
makes it harder to troubleshoot configuration issues in the healthcheck
endpoint, e.g DNS rebinding error. Printing the container logs helps the troubleshooting.

lib/mrsk/cli/healthcheck.rb

@@ -1,6 +1,8 @@
 class Mrsk::Cli::Healthcheck < Mrsk::Cli::Base
   MAX_ATTEMPTS = 5
 
+  class HealthcheckError < StandardError; end
+
   default_command :perform
 
   desc "perform", "Health check current app version"
@@ -18,7 +20,7 @@ class Mrsk::Cli::Healthcheck < Mrsk::Cli::Base
           if status == "200"
             info "#{target} succeeded with 200 OK!"
           else
-            raise "#{target} failed with status #{status}"
+            raise HealthcheckError, "#{target} failed with status #{status}"
           end
         rescue SSHKit::Command::Failed
           if attempt <= MAX_ATTEMPTS
@@ -31,7 +33,7 @@ class Mrsk::Cli::Healthcheck < Mrsk::Cli::Base
             raise
           end
         end
-      rescue SSHKit::Command::Failed => e
+      rescue SSHKit::Command::Failed, HealthcheckError => e
         error capture_with_info(*MRSK.healthcheck.logs)
 
         if e.message =~ /curl/