Wait for healthy containers in integration test

Rather than waiting 5 seconds and hoping for the best after we boot
docker compose, add docker healthchecks and wait for all the containers
to be healthy.

test/integration/docker/shared/Dockerfile

@@ -8,7 +8,10 @@ RUN mkdir ssh && \
   ssh-keygen -t rsa -f ssh/id_rsa -N ""
 
 COPY registry-dns.conf .
+COPY boot.sh .
 
 RUN mkdir certs && openssl req -newkey rsa:4096 -nodes -sha256 -keyout certs/domain.key   -x509 -days 365 -out certs/domain.crt   -subj '/CN=registry' -extensions EXT -config registry-dns.conf
 
-CMD ["bash", "-c", "cp -r * /shared"]
+HEALTHCHECK --interval=1s CMD pgrep sleep
+
+CMD ["./boot.sh"]

test/integration/docker/shared/boot.sh

@@ -0,0 +1,7 @@
+#!/bin/bash
+
+cp -r * /shared
+
+trap "pkill -f sleep" term
+
+sleep infinity & wait