fix(pubsub): Change UA_STATUSCODE_GOOD of retval at initialization
fix(pubsub): Change UA_STATUSCODE_GOOD of retval at initialization

 - Changed status code of retval to UA_STATUSCODE_BADNOTFOUND
   as the API functionality fails to invoke an error even a wrong
   publisherID is subscribed

Change-Id: I7c83223f5b964fb5dda818a3f202249c3cb257ce

JGrothoff/open62541,jpfr/open62541,JGrothoff/open62541,open62541/open62541,open62541/open62541,jpfr/open62541,open62541/open62541,jpfr/open62541,StalderT/open62541,StalderT/open62541,JGrothoff/open62541,JGrothoff/open62541,StalderT/open62541,StalderT/open62541,jpfr/open62541,open62541/open62541