Modified validation parameters for owner-uid and owner-gid.

owner-uid and owner-gid will not receive negative values anymore.

Change-Id: I82741d3d01b29e448294b2ec093fb70d22a5c77e
BUG: 912297
Signed-off-by: Avra Sengupta <asengupt@redhat.com>
Reviewed-on: http://review.gluster.org/4581
Reviewed-by: Amar Tumballi <amarts@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Anand Avati <avati@redhat.com>