Force deletes using tgt to workaround bug 1159948

Tgt has a bug where it can have multiple copies of an initiator
if there has been a reconnect.

See https://bugs.launchpad.net/cinder/+bug/1159948

Change-Id: I9a1b6757eb780efbaa1403016e50de7c0e45d720
(cherry picked from commit b84218633ab5417adf94c568eb54243f4074ab11)