Interpolation fix for network prediction

This is a minor fix for interpolation when playing online as predicted movement was not properly having its prev data reset like a real tick would be. This resulted in jittery player sprites in third person.

src/playsim/p_user.cpp

@@ -1481,6 +1481,8 @@ void P_PredictPlayer (player_t *player)
 			R_RebuildViewInterpolation(player);
 
 		player->cmd = localcmds[i % LOCALCMDTICS];
+		player->mo->ClearInterpolation();
+		player->mo->ClearFOVInterpolation();
 		P_PlayerThink (player);
 		player->mo->Tick ();