The default "full" tox environment excludes slow tests, while
full-parallel includes slow scenario tests. Some of them are certaintly
worth running (for example the encryption tests).
Depends-On: https://review.opendev.org/c/openstack/cinder/+/749155/
Change-Id: I1a916a49814b2f3e37b3455e6c4a318e1b2d7a6a