Cts lib, gracefully handle ble on mode

gms core can call enableBLE anytime. If this is being done just when the
scan setting is activated, the test may fail.
This will ensure that we allow and then disallow the scan setting only
during the wanted period of time.

Bug: 343871425
Flag: TEST_ONLY
Test: atest CtsBluetoothTestCases
Change-Id: I4ed69340de9fcd5fb96f58adeaee999a9a4cc4ee