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 b842186)

cinder/tests/test_iscsi.py

@@ -101,7 +101,8 @@ def setUp(self):
         self.flags(volumes_dir=self.persist_tempdir)
         self.script_template = "\n".join([
             'tgt-admin --update iqn.2011-09.org.foo.bar:blaa',
-            'tgt-admin --delete iqn.2010-10.org.openstack:volume-blaa'])
+            'tgt-admin --force '
+            '--delete iqn.2010-10.org.openstack:volume-blaa'])
 
     def tearDown(self):
         try:

cinder/volume/iscsi.py

@@ -190,7 +190,10 @@ def remove_iscsi_target(self, tid, lun, vol_id, **kwargs):
         else:
             raise exception.ISCSITargetRemoveFailed(volume_id=vol_id)
         try:
+            # NOTE(vish): --force is a workaround for bug:
+            #             https://bugs.launchpad.net/cinder/+bug/1159948
             self._execute('tgt-admin',
+                          '--force',
                           '--delete',
                           iqn,
                           run_as_root=True)