MFC r301871:

Add missing break in lock_partialfilelock(..) with NFS_RESERR

This will help ensure that the right error is trickled up when the
function is called if the lock status is NFS_RESERR

Tested with: fsx; svn info/svnversion (uses bdb locking); locktests from Bull http://nfsv4.bullopensource.org/tools/tests/locktest.php
CID: 1008161, 1304956