test/f: fix intelligent-host-selection/04

* Test works by overriding the background job runner so is not
  compatible with other job runners.

Author: oliver-sanders

tests/functional/intelligent-host-selection/04-kill.t

@@ -17,7 +17,7 @@
 #-------------------------------------------------------------------------------
 # Test job kill will retry on a different host if there is a connection failure
 
-export REQUIRE_PLATFORM='loc:remote fs:indep comms:tcp'
+export REQUIRE_PLATFORM='loc:remote fs:indep comms:tcp runner:background'
 . "$(dirname "$0")/test_header"
 
 #-------------------------------------------------------------------------------

tests/functional/intelligent-host-selection/04-kill/flow.cylc

@@ -3,7 +3,6 @@
     description = """
         Tasks
         - goodhost: a control to check that everything works
-        - badhost is always going to fail
         - mixedhost contains some hosts that will and won't fail
     """
 
@@ -18,7 +17,6 @@
     [[graph]]
         # Run good and mixed as controls
         R1 = """
-            goodhosttask & mixedhosttask
             goodhosttask:start => stop_g
             mixedhosttask:start => stop_m
         """