performance/write-behind: do not try to take LOCK in forget

LOCK attempt in wb_forget is unnecessary

Change-Id: Ibdedc23d0c829c34aedd6fc5bc0e0a584b832514
BUG: 903566
Signed-off-by: Raghavendra Bhat <raghavendra@redhat.com>
Reviewed-on: http://review.gluster.org/4423
Reviewed-by: Anand Avati <avati@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
 protocol/server: upon server_connection_put, set xl_private of the transport to
 NULL

 Suppose the get_xlator_by_name returns NULL and the connection is put back
 then update the xl_private of the transport by setting to NULL. Otherwise
 server_connection_put would have freed the connection object and xl_private
 of the transport would still be pointing to the same location which is
 freed, thus leading to a segfault when the location is accessed.

Change-Id: Id47e0edde3073b09765338c730847ba3095df9e2
BUG: 901457
Signed-off-by: Raghavendra Bhat <raghavendra@redhat.com>
Reviewed-on: http://review.gluster.org/4411
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Anand Avati <avati@redhat.com>