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
1 file changed