gpfs volume driver backup file access fixes

Changes to volume file permission settings require a temporary
chown to the file being backed up.

Also, use gpfs file clone copy mechanism to create a consistent
file copy so that the TSM backup service can create a hard link
to the clone file.

Closes-bug: 1286924

Change-Id: I951ab16788277d0052d1845fad963e9e4cdbc53e
Merge "gpfs volume driver backup file access fixes"