sets hardset_dna to clear exotic blood on race changes

sets every instance of race changes to use hardset_dna instead of directly replacing the datum (needs more testing to be sure I didn't break shit)
removes the invisible man race (aka the generic) and shadowlings from the new green slime mutation toxin while I'm in the area

code/game/objects/structures/mirror.dm

@@ -136,7 +136,7 @@
 			if(!newrace || !H.dna)
 				return
 
-			H.dna.species = new newrace
+			hardset_dna(H, null, null, null, null, newrace)
 
 			if(H.dna.species.use_skintones)
 				var/new_s_tone = input(user, "What are we again?", "Race change")  as null|anything in skin_tones