MP: 2p Silverhead Crossing - minor adjustments

- after the change to the tentacle, adjust HP to match 500 again
- let the teamname more sound like an easter egg
- apply the same lock settings as to similar scenarios

[ci skip]

data/multiplayer/scenarios/2p_Silverhead_Crossing.cfg

@@ -35,17 +35,21 @@
     [side]
         side=3
         team_name=nani
-        user_team_name= _ "teamname^Nani"
+        user_team_name= _ "teamname^Shapeshifter"
         color=black
-        controller=ai
+        controller=null
         allow_player=no
         disallow_observers=yes
         canrecruit=no
         no_leader=yes
         hidden=yes
+        controller_lock=yes
+        faction_lock=yes
+        leader_lock=yes
+        team_lock=yes
         [unit]
             type=Tentacle of the Deep
-            name= _ "Nani The Shapeshifter"
+            name= _ "Nani the Shapeshifter"
             x,y=1,1
         [/unit]
     [/side]
@@ -92,8 +96,8 @@
             [/effect]
             [effect]
                 apply_to=hitpoints
-                increase=472
-                increase_total=472
+                increase_total=475
+                heal_full=yes
             [/effect]
         [/object]
     [/event]