ganeti.cmdlib_unittest.py and
ganeti.cmdlib.instance_storage_unittest.py are moved to the
test/py/cmdlib directory. Also, they are renamed to match the names in
this module.

Additionally, instance_storage_unittest.py was added to the makefile, so
it's executed automatically during builds.

cmdlib_unittest.py now still contains tests from various cmdlib modules.
As soon as individual test files for those modules are added, those
tests should be move there.

Signed-off-by: Thomas Thrainer <thomasth@google.com>
Reviewed-by: Michele Tartara <mtartara@google.com>