Wait until Autofill sercvice is actually launched after enabling service.

In the test the config of Autofill service status sets synchronously,
but the launch of the service is done asynchronously after the setting
sets. And the delay of launch sometimes caused flakiy failures.

This CL adds the code to wait for the service launch after changing the
status of Autofill service.

Bug: 134662826
Test: Ran the entire CtsAutoFillServiceTestCases on eve:
    'cts-tradefed run command cts --module CtsAutoFillServiceTestCases'
Test: Ran PartitionedActivityTest#testAutofillBundleDataIsPassedAlong
    with cts-tradefed 100 times on eve
Change-Id: Id3443cedf3dbaf75b88bf15688d73eee8385902e
Merged-In: Id3443cedf3dbaf75b88bf15688d73eee8385902e