Wait for the looper to be acquired

TestLooperManager post a message on the looper, client using post a
message in front of queue can race with it and in some case, it end up
running before the looper is acquired.

Bug: 430185336
Test: atest ModulesUtilsTests
Test: atest StateMachineTest
Test: atest testStateMachineQuitNowAfterStart --rerun-until-failure 100
Flag: TEST_ONLY
Change-Id: I13783e93aa5103bd0b24cee8a9e9d84815aa8472