Request pipeline: remove FIXME
Request pipeline: remove FIXME

I checked everything that uses the request pipeline (directly or
indirectly), and nothing checks for error codes outside of those
specified in XMPP Core. (Previously this code used
gabble_message_get_xmpp_error, which would also fetch Jingle, SI and a
couple of other class of error.)

Ziemin/telepathy-gabble,mlundblad/telepathy-gabble,Ziemin/telepathy-gabble,mlundblad/telepathy-gabble,mlundblad/telepathy-gabble,Ziemin/telepathy-gabble,Ziemin/telepathy-gabble