Fix VTS testLockTaskAfterReboot_deviceOwnerUser

1. testLockTaskAfterReboot_deviceOwnerUser accesses window manager service
   before booting is completed then it causes test failed.

2. This change makes VTS wait until booting is completed.

Test: run cts-on-gsi -m CtsDevicePolicyManagerTestCases -t testLockTaskAfterReboot_deviceOwnerUser

BUG : 128479977

Change-Id: Ib39babd85acb6c611f590c42fcff24c663b1c355
diff --git a/hostsidetests/devicepolicy/src/com/android/cts/devicepolicy/DeviceOwnerTest.java b/hostsidetests/devicepolicy/src/com/android/cts/devicepolicy/DeviceOwnerTest.java
old mode 100755
new mode 100644
index 28dd552..28ec255
--- a/hostsidetests/devicepolicy/src/com/android/cts/devicepolicy/DeviceOwnerTest.java
+++ b/hostsidetests/devicepolicy/src/com/android/cts/devicepolicy/DeviceOwnerTest.java
@@ -538,7 +538,7 @@
                     mPrimaryUserId);
 
             // Reboot while in kiosk mode and then unlock the device
-            getDevice().reboot();
+            rebootAndWaitUntilReady();
 
             // Check that kiosk mode is working and can't be interrupted
             runDeviceTestsAsUser(DEVICE_OWNER_PKG, ".LockTaskHostDrivenTest",