Following neutron change If44bfef9428f43dd82758928bf46786b70e5e11c
we need to use set_extra_attr_value (for each extra attribute)
instead of _process_extra_attr_router_create
We also skip the pagination tests - need to try and figure out
what has broken us there. This may be:
https://review.openstack.org/420394
A revert for the paginationc hange is also in review.
Change-Id: I1e58f52538824a086923b1e0c3d1ce1217c0aae0