Add Nova API Sample file & test for get keypair

This patch adds the new API Sample file and its test for Nova V2 and V3
get keypair APIs.

This patch extend the timstamps reg exp to allow the combination
of TZ and microsecond/

Closes-Bug: 1298769
Closes-Bug: 1298818

Change-Id: If695a23cf95862b7bec6fbc5bdf7fc1733d08d4a
Merge "Add Nova API Sample file & test for get keypair"