Set audio volumes before entering main loop

Fixes an issue where the volumes would be at max before the first wipe
finishes. This is because S_UpdateSounds isn't called during wipes.

src/d_main.cpp

@@ -894,6 +894,12 @@ void D_SRB2Loop(void)
 	because I_FinishUpdate was called afterward
 	*/
 
+	// Make sure audio volume is initialized since S_UpdateSounds won't be called during the
+	// initial wipe.
+	S_SetMasterVolume();
+	S_SetMusicVolume();
+	S_SetSfxVolume();
+
 	for (;;)
 	{
 		// capbudget is the minimum precise_t duration of a single loop iteration