Philipp Hörist authored Mar 24, 2018 and Philipp Hörist committed Mar 26, 2018

For MUCs on the blacklist we do a deduplication not depending on
stanza-id

This patch is only for current Prosody 0.10 stable and the mod_mam_muc
module which does not add stanza-id to the messages.

This can be removed once Prosody 0.11 hits or the module is updated