Unify comm.lua's is_ssl and shortport.ssl

Heuristic detection of SSL ports was previously done in 2 different
places, leading to a divergence: shortport.ssl would return true for
more services than comm.tryssl would try, since comm.is_ssl was checking
a shorter list of port numbers and was ignoring
port.version.service_tunnel and port.version.name. Now any changes to
shortport.ssl will affect both libraries.