Refactor: executor,libcrmservice: parse OCF exit reasons in service library

Previously, the executor parsed exit reasons from the service library's stderr
output. Now, since the service library action type tracks an exit reason
itself, parse it there instead.

This does change behavior slightly:

Previously, the executor would attempt to parse the exit reason regardless of
the action standard in use, and regardless of the action result. Now, the
service library parses the exit reason only for OCF agents that produce error
output (which is the only case that matters).

Parsing in the executor also meant that other callers, such as crm_resource,
could not get the OCF exit reason. Now, they can.