presence-cache: fix disco_in_progress
presence-cache: fix disco_in_progress

Embarrassingly this has never worked and I've surprised it didn't
crash. The priv->disco_pending hash table is in fact:

  GHashTable<gchar*,GList<DiscoWaiter*>> disco_pending;

but the previous disco_is_pending assumed it was:

  GHashTable<gchar*,DiscoWaiter*> disco_pending;

Oops!

Signed-off-by: Jonny Lamb <3d1fb3642aaab2ff70e3392a5ab916bf99eed6a3@collabora.co.uk>

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