glusterd: Returning success from mgmt_v3 handler functions

The mgmt_v3 handler functions already send the ret code as
part of the *send_resp calls, and further propagating the
ret code to the calling functions will lead to double deletion
of the req object. Hence returning success from the mgmt_v3
handler functions.

Change-Id: I1090e49c54a786daae5fd97b5c1fbcb5d819acba
BUG: 1138577
Signed-off-by: Avra Sengupta <asengupt@redhat.com>
Reviewed-on: http://review.gluster.org/8620
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Krishnan Parthasarathi <kparthas@redhat.com>
Tested-by: Krishnan Parthasarathi <kparthas@redhat.com>