Fixed a problem in iSCSI multipath

Multipathing for attach volume and detach volume operations
doesn't work properly if there are different targets
associated with different portals for a mulitpath device.

Change-Id: Iab316526cf64de60325d90043f73fa3e83fafb4e
Closes-Bug: #1266051
Merge "Fixed a problem in iSCSI multipath"