762989.t: fix a typo by grepping only the blocked port number from netstat o/p

Change-Id: I14c3daa799f0936014bf8aa9fd798ecbaec6e912
BUG: 762989
Signed-off-by: Raghavendra Bhat <raghavendra@redhat.com>
Reviewed-on: http://review.gluster.org/4426
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Anand Avati <avati@redhat.com>