website: routing_setup() as pytest fixture

website: routing_setup() as pytest fixture

c80e9d2118ca5bcdec5285898a532f8e18faa6b6 had removed the use of
routing_setup() without adding a fixture to replace it. this had broken
routing_check(), but we hadn't noticed it because pytest hadn't
supported the 'yield' pattern in test_routing_generator() to call it

test_routing_generator() now uses this routing_setup fixture to provide
the kwargs that had previously been injected into routing_check() via
@common.with_setup_kwargs(setup=routing_setup, teardown=routing_teardown)

Signed-off-by: Casey Bodley <cbodley@redhat.com>