Rerun os-collect-config if config changed

Keep a hash of the config file for os-collect-config and if it changes
during a failed run then rerun immediately(without sleep), effectively
causing new nodes to be ready 5 minutes earlier.

Because the cfn credentials are placed into os-collect-config.conf by
os-apply-config and are not in place the first time os-collect-config is
run, the first run of os-collect-config results in error, o-c-c then
sleeps for 5 minutes before running successfully the second time.

Fixes bug #1219186

Change-Id: I090de7a3d84e0ea342f1a422646c0c455eb37f4a