Sync turnobjs for polyrotate_t thinkers in netgames

This fixes an apparent "desync" that LJ Sonic has been telling me and others about for a while now. Turns out rotating polyobjs (such as those in one part of CEZ2) did not sync whether they turned objects or not in netgames, if someone joined mid-level. This means if a polyobject was supposed to turn the player according to linedef flags, it possibly does not for the person who joined!

This bug would have been present in 2.1 as well, except you didn't get rotating polyobjects all that often back then so no one would have noticed. It's no wonder we only found out about it now.