glusterd: Removed 'proactive' failing of volume op

Volume operations were failed 'proactively', on the first disconnect of
a peer that was participating in the transaction.

The reason behind having this kludgey code in the first place was to
'abort' an ongoing volume operation as soon as we perceive the first
disconnect. But the rpc call backs themselves are capable of injecting
appropriate state machine events, which would set things in motion for an
eventual abort of the transaction.

Change-Id: Iad7cb2bd076f22d89a793dfcd08c2d208b39c4be
BUG: 847214
Signed-off-by: Krishnan Parthasarathi <kparthas@redhat.com>
Reviewed-on: http://review.gluster.org/4869
Reviewed-by: Jeff Darcy <jdarcy@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>