Bump oslo.config version

There is a bug in oslo.config <=1.3.0 when registering cli opts with
deprecated_opts set. This causes an error with registering the oslo.db
opts. The bug was fixed post 1.3.0, so pinning this to >= the latest
alpha, which will pull in any release 1.4.0 when it becomes available.

Closes-Bug: #1347911

Change-Id: I58505ffcdfb0acf0ed2137282c18258e94e201f6