tests: Change DISP before start main sec tests

So is possible to change the values

test/test_main_sec.py

 from time import sleep
 
-from epics import caget
+from epics import caget, caput
 from helper import change_state, check_readback
 
 class TestMainSec:
     def test_main(self, prefix):
+        caput(prefix + ":MAIN.DISP", 0)
         for state in ["RESET", "INIT"]:
             assert change_state(prefix, state)
-
+        
         assert check_readback(prefix + ":MAIN", 1)
 
         assert check_readback(prefix + ":VMENBL", 1)