Fix docker-healthcheck to work around Docker bug.

This is a workaround to better detect moby/moby#38642 when Docker starts
up and remains stuck.  In this case `docker ps` will return nothing and
exit 0, but no container can actually start.  A better (but more expensive
and more intrusive test) would be to `docker run --rm` some cheap test
container to confirm we can actually start a container.

upup/models/nodeup/docker/_systemd/_debian_family/files/opt/kubernetes/helpers/docker-healthcheck

@@ -17,7 +17,19 @@
 # This script is intended to be run periodically, to check the health
 # of docker.  If it detects a failure, it will restart docker using systemctl.
 
-if timeout 60 docker ps > /dev/null; then
+healthcheck() {
+   if output=`timeout 60 docker network ls`; then
+       echo "$output" | fgrep -qw host || {
+          echo "docker 'host' network missing"
+          return 1
+       }
+   else
+       echo "docker returned $?"
+       return 1
+   fi
+}
+
+if healthcheck; then
   echo "docker healthy"
   exit 0
 fi
@@ -26,7 +38,7 @@ echo "docker failed"
 echo "Giving docker 30 seconds grace before restarting"
 sleep 30
 
-if timeout 60 docker ps > /dev/null; then
+if healthcheck; then
   echo "docker recovered"
   exit 0
 fi
@@ -43,7 +55,7 @@ systemctl start docker
 echo "Waiting 120 seconds to give docker time to start"
 sleep 60
 
-if timeout 60 docker ps > /dev/null; then
+if healthcheck; then
   echo "docker recovered"
   exit 0
 fi