bugfix: Hardmode grenades do not work on enemies with less than 80% HP (

#6080)

* bugfix: Hardmode grenades do not work on enemies with less than 80% HP

* Made initial enrage() return true if enraged successfully

code/modules/mob/living/simple_animal/hostile/megafauna/ancient_robot.dm

@@ -172,6 +172,9 @@ Difficulty: Very Hard
 
 /mob/living/simple_animal/hostile/megafauna/ancient_robot/enrage()
 	. = ..()
+	if(!.)
+		return
+
 	armour_penetration = 66
 	TL.armour_penetration = 66
 	TR.armour_penetration = 66

code/modules/mob/living/simple_animal/hostile/megafauna/blood_drunk_miner.dm

@@ -288,6 +288,9 @@ Difficulty: Medium
 
 /mob/living/simple_animal/hostile/megafauna/blood_drunk_miner/enrage()
 	. = ..()
+	if(!.)
+		return
+
 	miner_saw = new /obj/item/melee/energy/cleaving_saw(src) //Real saw for real men.
 	dash_cooldown_to_use = 0.5 SECONDS //Becomes a teleporting shit.
 	ranged_cooldown_time = 5 //They got some cooldown mods.

code/modules/mob/living/simple_animal/hostile/megafauna/bubblegum.dm

@@ -125,6 +125,9 @@ Difficulty: Hard
 
 /mob/living/simple_animal/hostile/megafauna/bubblegum/enrage()
 	. = ..()
+	if(!.)
+		return
+
 	maxHealth = 2000 //Less health, as a phase 2
 	health = 2000
 	rapid_melee = 12 //Don't stand still

code/modules/mob/living/simple_animal/hostile/megafauna/colossus.dm

@@ -108,6 +108,9 @@ Difficulty: Very Hard
 
 /mob/living/simple_animal/hostile/megafauna/colossus/enrage()
 	. = ..()
+	if(!.)
+		return
+
 	move_to_delay = 5
 
 /mob/living/simple_animal/hostile/megafauna/colossus/unrage()

code/modules/mob/living/simple_animal/hostile/megafauna/hierophant.dm

@@ -123,6 +123,9 @@ Difficulty: Hard
 
 /mob/living/simple_animal/hostile/megafauna/hierophant/enrage()
 	. = ..()
+	if(!.)
+		return
+
 	move_to_delay = 5
 
 /mob/living/simple_animal/hostile/megafauna/hierophant/unrage()

code/modules/mob/living/simple_animal/hostile/megafauna/megafauna.dm

@@ -219,8 +219,10 @@
 /// This proc is called by the HRD-MDE grenade to enrage the megafauna. This should increase the megafaunas attack speed if possible, give it new moves, or disable weak moves. This should be reverseable, and reverses on zlvl change.
 /mob/living/simple_animal/hostile/megafauna/proc/enrage()
 	if(enraged || ((health / maxHealth) * 100 <= 80))
-		return
+		return FALSE
+
 	enraged = TRUE
+	return TRUE
 
 /mob/living/simple_animal/hostile/megafauna/proc/unrage()
 	enraged = FALSE