Cisco VPN device driver post-merge cleanup

Cisco VPN device driver post-merge cleanup

During review for I-3 there were some minor comments regarding log
level on message and asserts for mock calls.

In addition, some debug logging enhancements were made between the
service and device driver to better indicate the source of the
shared "vpnservice_updated" RPC.

Lastly, unit tests were updated, based on a newer Cisco CSR image,
which had REST API fixes and behavior changes.

Change-Id: I22277462270df0b2cd642ec576e8652c9df146b5
Closes-bug: 1288387