When registering a job with a service and 'consul.allow_unauthenticated=false',
we scan the given Consul token for an acceptable policy or role with an
acceptable policy, but did not scan for an acceptable service identity (which
is backed by an acceptable virtual policy). This PR updates our consul token
validation to also accept a matching service identity when registering a service
into Consul.
Fixes#15902
Seth Hoenig