glusterd: Fix incorrect remove-brick status

PROBLEM:

'remove-brick status' was reported to be showing the status
of a previous rebalance op that was aborted, on the node which
doesn't participate in the remove-brick operation.

FIX:

Unconditionally reset defrag status to NOT_STARTED whenever a
remove-brick or a rebalance op is attempted.

Change-Id: Iddf3a14a2ef352e77e0f690fe65aa36ec3011257
BUG: 1040371
Signed-off-by: Krutika Dhananjay <kdhananj@redhat.com>
Reviewed-on: http://review.gluster.org/6482
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Krishnan Parthasarathi <kparthas@redhat.com>
Reviewed-by: Kaushal M <kaushal@redhat.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>