Import and convert to oslo loopingcall.

Import the oslo looping call implementation (which is a copy of
nova's), delete nova's local copy, convert all users to the new
location.

It should be noted that the oslo implementation of
FixedIntervalLoopingCall measures time from the start of the
periodic task, not the end, so periodic tasks will run with a
constant frequency instead of the frequency changing depending on
how long the periodic task takes to run.

Change-Id: Ia62ce1988f5373c09146efa6b3b1d1dc094d50c4
Add unit tests for /db/api.py#fixed_ip_*

Implements: some tests for db methods fixed_ip_* for blueprint db-api-tests
Change-Id: I51fe24600b7df2b529350ad70939a01f60bd3c9c
Merge "Add unit tests for /db/api.py#fixed_ip_*"
Merge "Import and convert to oslo loopingcall."