bridge: Make test-metrics helpers more universal
bridge: Make test-metrics helpers more universal

Change `recv_{bytes,object,array}()` to directly take a MockTransport,
instead of a TestCase, so that they can be used with tests that don't
use setup().

deryni/cockpit,martinpitt/cockpit,deryni/cockpit,cockpit-project/cockpit,deryni/cockpit,mvollmer/cockpit,deryni/cockpit,moraleslazaro/cockpit,mvollmer/cockpit,mvollmer/cockpit,garrett/cockpit,martinpitt/cockpit,cockpit-project/cockpit,cockpit-project/cockpit,deryni/cockpit,garrett/cockpit,moraleslazaro/cockpit,garrett/cockpit,martinpitt/cockpit,mvollmer/cockpit,deryni/cockpit,garrett/cockpit,moraleslazaro/cockpit,moraleslazaro/cockpit,martinpitt/cockpit,martinpitt/cockpit,garrett/cockpit,deryni/cockpit,moraleslazaro/cockpit,mvollmer/cockpit,cockpit-project/cockpit,moraleslazaro/cockpit,cockpit-project/cockpit,moraleslazaro/cockpit