Fixes air tank and similar item sprites in suit storage slot for Teshari. (#4608)

Overlooked in last air tank fix PR.
Suit storage sprites can now be defined per-species if the need arises for anything as weird as Tesh. That method seemed neater than a bit of unique code just for Teshari in the base update_icons code.

code/modules/mob/living/carbon/human/species/species.dm

@@ -15,6 +15,7 @@
 
 	var/speech_bubble_appearance = "normal"              // Part of icon_state to use for speech bubbles when talking.  See talk.dmi for available icons.
 	var/fire_icon_state = "humanoid"                     // The icon_state used inside OnFire.dmi for when on fire.
+	var/suit_storage_icon = 'icons/mob/belt_mirror.dmi'  // Icons used for worn items in suit storage slot.
 
 	// Damage overlay and masks.
 	var/damage_overlays = 'icons/mob/human_races/masks/dam_human.dmi'

code/modules/mob/living/carbon/human/species/station/seromi.dm

@@ -33,6 +33,7 @@
 	damage_overlays = 'icons/mob/human_races/masks/dam_seromi.dmi'
 	damage_mask = 'icons/mob/human_races/masks/dam_mask_seromi.dmi'
 	blood_mask = 'icons/mob/human_races/masks/blood_seromi.dmi'
+	suit_storage_icon = 'icons/mob/species/seromi/belt_mirror.dmi'
 
 	fire_icon_state = "generic" // Humanoid is too big for them and spriting a new one is really annoying.
 

code/modules/mob/living/carbon/human/update_icons.dm

@@ -875,7 +875,7 @@ var/global/list/damage_icon_parts = list()
 	if(s_store)
 		var/t_state = s_store.item_state
 		if(!t_state)	t_state = s_store.icon_state
-		overlays_standing[SUIT_STORE_LAYER]	= image("icon" = 'icons/mob/belt_mirror.dmi', "icon_state" = "[t_state]")
+		overlays_standing[SUIT_STORE_LAYER]	= image("icon" = species.suit_storage_icon, "icon_state" = "[t_state]")
 		s_store.screen_loc = ui_sstore1		//TODO
 	else
 		overlays_standing[SUIT_STORE_LAYER]	= null