IPv6 healthcheck fixes for nova-vnc-proxy

In case of IPv6 URLs brackets are required. This adds a check for IPv6 and
adds brackets if needed.

Change-Id: If0931c605c92adc74c9a743faacff56cbe5db7f5

healthcheck/nova-vnc-proxy

@@ -12,4 +12,9 @@ if [ "${proto_is_ssl,,}" = true ] ; then
     bind_proto=https
 fi
 
+# Add brackets if IPv6
+if [[ $bind_host =~ ":" ]]; then
+    bind_host="[${bind_host}]"
+fi
+
 healthcheck_curl ${bind_proto}://${bind_host}:${bind_port}/