Log Request ID Mappings

Tracking requests across multiple OpenStack services is difficult.
This is a proposal for logging corresponding request IDs together, so users
can easily lookup the request IDs of services other than the one the user
called directly.

blueprint log-request-id-mappings

Change-Id: Ib9b820a0feeb0c0e828ed3e4fab8261f8761ba9a
Merge "Log Request ID Mappings"