Rename oslo.concurrency to oslo_concurrency

oslo.concurrency-0.3.0 has moved its path to oslo_concurrency,
the old path oslo.concurrency can still work but is deprecated now.

Closes-Bug: #1398656
Change-Id: I52211d7b7e1db3454c99d27042dae506adb2c41c
Merge "Rename oslo.concurrency to oslo_concurrency"