Add testrepository build dep to oslo.context
Add testrepository build dep to oslo.context

oslotest has dropped its runtime dependency on testrepository[1] but
this package still relies on it, so add it as a build dependency until
it switches to stestr.

[1] https://review.openstack.org/569914

Change-Id: I37f9f57db57ec9256d87c908e28f70e634cec0d8

openstack/rpm-packaging,openstack/rpm-packaging