Northern Rebirth S02_01: keep side 8 leader from wandering off too far

If he ends up on the tiny keep in the south, he can only recruit one
unit per turn, which affects the intended balance of the scenario.
Fixes #3073

(cherry-picked from commit 9b9aa13a3d)

data/campaigns/Northern_Rebirth/scenarios/02_01_Infested_Caves.cfg

@@ -266,6 +266,20 @@
         [/message]
     [/event]
 
+    # Keep Mal Tath from grabbing the southern-most village and ending up on
+    # the tiny castle in the south during the first two turns
+    [event]
+        name=side 8 turn 1 refresh, side 8 turn 2 refresh
+        first_time_only=no
+
+        [modify_unit]
+            [filter]
+                id=Mal Tath
+            [/filter]
+            moves=4
+        [/modify_unit]
+    [/event]
+
     # Find Camerin event
     [event]
         name=capture