docker: correctly compare 'command' param against existing container command'

If a container has an "entrypoint" in addition to a "command", the Docker API will return "{} {}".format(entrypoint, command) for the value of 'Command' in the container summary JSON. This checks if a container's 'Command' value **ends with** module.params('command') instead of equals it so that containers with entrypoints are correctly classified as match the module's argument spec. (I think this is what caused #6395, and should fix it)