Ensure package-wide test init is done with testr

This patch adds testresources.ResourcedTestCase as another base class
for compute and boto tests. This allows us to perform package-wide
init for tests when running them under testr. The init was not being
performed when the tests were run under testr because setup_package is
a nosetests specific init feature. The setup_package functions in
__init__.py files are renamed to ensure that the initialisation is
only done once.

Implements: blueprint speed-up-tempest
Change-Id: If76f71cb06f2243607db2680504e94dc65e1f585
Merge "Ensure package-wide test init is done with testr"