Refactor tests/base.py not to import objects but modules
Refactor tests/base.py not to import objects but modules

This patch modifies tests/base.py to import the modules instead of the
objects.

Change-Id: Id1a3720886cb2db5186af0cf3d0436c59063b5e7
Signed-off-by: Taku Fukushima <d385cb54d860d8a5dcc6157b54cf213091772451@gmail.com>

openstack/kuryr,midonet/kuryr,openstack/kuryr,midonet/kuryr,celebdor/kuryr-libnetwork,midonet/kuryr,celebdor/kuryr,celebdor/kuryr-libnetwork,celebdor/kuryr-libnetwork,celebdor/kuryr