Add extra logic to handle port detach issue

nova manager will first delete local neutron port before call driver to
detach port on PowerVC. This behavior will trigger a local port deleted
event and cause current driver code failed to retrieve remote PowerVC
port id when doing interface detach

1. First priority is to use local port id to retrieve remote PowerVC
port id, which is the current logic.
2. If local port id cannot be retrieved, it will call interface_list on
remote PowerVC instance and get all attached interface information. Then
the code will scan all the local port IP addresses and compare to remote
IP addresses and find the matched port id to detach.

Change-Id: I3a87f3780c2cb949a0dc80380a37ab17bb98e059
Closes-Bug: #1392540
(cherry picked from commit 8c766d08616b30dae4712f0a586adb28604725d6)