Change to nose2

Use nose2 instead of stestr for running unit test as nose2 provides
junit-style xml output that can be reported in Jenkins to show test
pass/fail and trend history.

Change-Id: I3f57992ca7252bfd5403f7fdf7153d1faa232e71
Signed-off-by: beierl <mbeierl@vmware.com>
4 files changed