Remove usage of pbr

Anvil has conflicts with pbr when it's used in setup.py
and its usage in anvil doesn't really seem useful or applicable
given the amount of pain it causes during packaging and later pip
usage (dependencies downloaded and introspected will themselves
fail due to the wrong version of pbr that anvil pulled in).

So instead of using it, just switch back to using a simpler
setup.py file with usage of nosetests for testing (since we
don't need parallel tests for anvils tests) to avoid the
problems that pbr has caused.

Change-Id: I6d3c09a927434abf07fc025638a0860e44b029fa