Make IPDB and IPRoute calls indirect
Make IPDB and IPRoute calls indirect

This patch moves the instantiations of IPDB and IPRoute to the module
level functions to avoid them from reading Linux specific files, which
were preventing Mac OSX users from running the unit tests.

Change-Id: Id6ac74756aab6250bf1fdab817c984a866180d59
Signed-off-by: Taku Fukushima <d385cb54d860d8a5dcc6157b54cf213091772451@gmail.com>
Closes-Bug: #1546400

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