Added missing accept_transfer to FC

The base class FibreChannelDriver was
missing the new accept_transfer method.
This was caught while running the devstack
driver certification tests again the
3PAR FC driver.
This patch adds the missing method to the
base VolumeDriver.

Change-Id: I0aa91a4f11edd03eee7607d15317b89c30732cb7
Closes-Bug: #1269633
Merge "Added missing accept_transfer to FC"