mod_s2s_keepalive: Fix response handler (thanks Ge0rG) So there are no 'iq-{result,error}/host' events, mod_iq only fires events for result stanzas that include the full 'id' attr. This fixes it by hooking the stanza router event.

---
summary: Allow server administrators to probe any user
...

This module lets server administrators send `<presence type="probe"/>`
to any local user and receive their presence in response, bypassing
roster checks.