Guarantee patrole tempest gate run times to under 1 hour

QA, at the PTG, requested that our Patrole gates run underneath an hour. Right now, we are encroaching upon that threshold. Thus, various strategies should be used to decrease the overall gate run time.

1) As part of this blueprint, a list needs to be compiled with the slowest tests. Many of those tests will probably include compute tests. Currently, there are several compute rbac test files that can be merged together, to reduce the number of servers that are booted. For example, test_lock_server_rbac and test_suspend_server_rbac can probably be merged together in the same file, i.e. test_server_actions_rbac.

The same sort of approach may need to be taken for volume tests, which are very slow, particularly those involving backups.

2) The test regex used to kick off tempest tests should be modified to look something like:
tempest run --regex (?!.*\[.*\bslow\b.*\])(^patrole_tempest_plugin\.(api|scenario))

It may be needed to tag slow tests just like Tempest does (see regex above), and run those slow tests using a separate command. Additional tempest gates can be added to run those slow tests on their own, if need be.

3) Only tests included in the big tent services [0] should be included in Patrole; tests belonging to other services should create a Patrole plugin.

Additionally, we probably need to hold off on implementing any further slow tests (i.e. shelve compute tests) until we have completed this blueprint.

[0] https://github.com/openstack/tempest/tree/master/tempest/api