TpConnectionManager: ref the TpCM while NameOwnerChanged is processed
TpConnectionManager: ref the TpCM while NameOwnerChanged is processed

Previously, tp_connection_manager_end_introspection could sometimes
result in losing the last reference, and a crash.

Distrotech/telepathy-glib,Distrotech/telepathy-glib,Distrotech/telepathy-glib,Distrotech/telepathy-glib,Distrotech/telepathy-glib