Use default rpc_response_timeout in unit tests
Use default rpc_response_timeout in unit tests

During running of tox the system can timeout on slower systems.
We have seen this occur in our internal tests and have seen
better results when we increased the api timeout from 15 to 60
seconds.  This can be used until faster hardware is availale
or a better fix is proposed.  Andrew Laski first proposed
this fix.

Closes-Bug: 1311778

Change-Id: I33da328e7bea8fbdde3f01ee0147b4c5a3a278d2

citrix-openstack-build/oslo.versionedobjects,openstack/oslo.versionedobjects