BUG/MEDIUM: hlua: Don't call RESET_SAFE_LJMP if SET_SAFE_LJMP returns 0.

If SET_SAFE_LJMP returns 0, the spinlock is already unlocked, and lua_atpanic
is already set back to hlua_panic_safe, so there's no need to call
RESET_SAFE_LJMP.

This should be MFC'd into 1.8.
diff --git a/src/hlua.c b/src/hlua.c
index 67bc93c..f07df47 100644
--- a/src/hlua.c
+++ b/src/hlua.c
@@ -6391,7 +6391,6 @@
 			error = "critical error";
 		SEND_ERR(px, "Lua applet tcp '%s': %s.\n",
 		         ctx->rule->arg.hlua_rule->fcn.name, error);
-		RESET_SAFE_LJMP(hlua->T);
 		return 0;
 	}