Enhance v3 list_services to test filtering by service type

Initially included in the patch [0], the API test for
testing correct filtering by identity v3 list_services is
implemented by this commit.

This will also help to avoid the error of the wrong
uri being passed to GET in list_services which was fixed
by [1].

[0] https://review.openstack.org/#/c/461236/3
[1] I2e2ebb72732ab95d5f9c1d988037c5e263bf2a71

Change-Id: I5fed1dea0e878911961e6ae0fa8edbffab8195b4
1 file changed