port test_keypairs into nova v3 part1

This changeset only copies the v2 files into the appropriate v3
directories unchanged. This is being tried in order to make
reviewing of the porting easier as gerrit will display only what
is actually changed for v3 rather than entirely new files.

Partially implements blueprint nova-v3-api-tests

Change-Id: I1f49bb12cb193bfa7db069f392f845838d6f8cc4
Add test_discover module to provide a load_tests hook

This commit adds a load_tests hook that will be used to discover the
set of tempest tests that excludes the unit tests. We can't just
discover from the tempest topdir like we previously did because of
mutually exclusive requirements between the normal tempest tests and
the unit tests. (for example mox and mock should not be required for
a tempest run)

Change-Id: I562f033d78e654675fd77af3bf64c44945127bd7
Merge "Add test_discover module to provide a load_tests hook"
Merge "port test_keypairs into nova v3 part1"