Fixes taking control of crit xenos (#4536)

# About the pull request

Alright so I did not consider that *all* xenos that did not have a
client and could be taken over would be considered unconscious.

# Explain why it's good for the game

Uuuh you should be able to join as a xeno...


# Testing Photographs and Procedure
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<summary>Screenshots & Videos</summary>

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screenshots and the `<details>` tags.

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# Changelog

:cl: Morrow
fix: Fixed taking control of crit xenos
/:cl:

code/game/gamemodes/cm_initialize.dm

@@ -446,7 +446,7 @@ Additional game mode variables.
 			to_chat(xeno_candidate, SPAN_WARNING("You cannot join if the xenomorph is dead."))
 			return FALSE
 
-		if(new_xeno.stat == UNCONSCIOUS)
+		if(new_xeno.health <= 0)
 			to_chat(xeno_candidate, SPAN_WARNING("You cannot join if the xenomorph is in critical condition or unconscious."))
 			return FALSE