blindfold_enabled => skip_replay enabled, in playmp_controller

this was suggested by Wintermute, as it is hard to see why you
wouldn't want the replays to go fast if you can't see anything.
workaround for bug #21797

when the side engine in multiplayer_connect_engine.cpp loads a side,
if the game is a save game, the side is not allowed to have a human
player, and it is listed as "network", then we set it to ai,
assuming that it "should" be a "network_ai" if bug #18829 is ever
fixed
Merge branch '1.12' of https://github.com/wesnoth/wesnoth into 1.12