Do not send automatic unavailable presence if initial presence was not

This is related to #89, but there is another problem so I'm not closing it yet.

Signed-off-by: Daniele Ricci <daniele.athome@gmail.com>
Remove from attribute from iq stanzas when they are from a resolver

Signed-off-by: Daniele Ricci <daniele.athome@gmail.com>