Latching not working for VanillaDockerApplications built on hub images

[johnmccabe]

If you build a VanillaDockerApplication on top of a docker hub image which is configured to start on run (ie has an entrypoint) then none of the provided latch points are suitable to prevent the container from running when provisioned (even the provision latch).

Currently you have to make use of the env: tag to create a latch that blocks creation (and running) of the container.

For example:

env:
  DUMMY_LATCHING_VAR: $brooklyn:component("global", "my-latched-on-entity").attributeWhenReady("service.isUp")