Only call register_service_clients if there are clients

Right now we unconditionally run register_service_clients() on each
plugin regardless of whether there are any clients or not. This can lead
to false tracebacks being logged if there is any error reported in the
call path, regardless of whether the plugin is at fault or not. To
avoid this potential confusion this commit changes the registry call to
only occur if there are any clients we actually want to register. If
there aren't any we just skip that plugin.

Change-Id: I526d4acd99bbcfbf27c4090391f341bc61fdb194
2 files changed