rend_service_relaunch_rendezvous() ignores hs_service_requires_uptime_circ()

rend_service_introduce() sets CIRCLAUNCH_NEED_UPTIME in flags if rend_service_requires_uptime() is true.

But rend_service_relaunch_rendezvous() doesn't do this.

We should do the same thing in both places, or, better yet, we should refactor the code so it's shared.