SPY-145: Make OperationImpl inline properly.

Change-Id: Ia03701670d9b3bb82d7e8c4798dd5cb99c9e25c7
Reviewed-on: http://review.couchbase.org/30418
Reviewed-by: Michael Nitschinger <michael.nitschinger@couchbase.com>
Tested-by: Michael Nitschinger <michael.nitschinger@couchbase.com>