Change rsModAVUMetadata to call acPostProcForModifyAVUMetadata only if
the chlSetAVUMetadata call succeeds.  This was recommended by Tony
Edgin of iPlant on irods-chat and matchs a recent change for 
rsModAccessControl.

Also, as done for rsModAccessControl, reformatted/adjusted a little
and removed some comments.  In this case, I think it was fine to have
some comments in the source explaining a change made by a particular
developer for a while, but long term, I think it's easier to read the
code if we use svn for maintaining such information.



git-svn-id: svn://irodssvn.ucsd.edu/trunk@5588 ea137bd6-aa86-47b6-b90d-b101d9f19a90