tests/dbus/connection.c: add a simple regression test for mapping user-requested disconnection to TP_ERROR_CANCELLED
tests/dbus/connection.c: add a simple regression test for mapping user-requested disconnection to TP_ERROR_CANCELLED

This goes via the old code path in TpConnection, using the status
reason.

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