Reduce unnecessary Handler processing.

MSG_CHECK_JOB, MSG_CHECK_JOB_GREEDY, and MSG_JOB_EXPIRED all force
queuing ready jobs in at least one code path. There can be situations
where all and/or multiple messages are in the handler queue, which
become unnecessary and redundant when we enqueue ready jobs. Remove all
extraneous messages so we don't do unnecessary repetitive processing.

Bug: 166701460
Test: atest CtsJobSchedulerTestCases
Test: atest FrameworksMockingServicesTests:ConnectivityControllerTest
Test: atest FrameworksMockingServicesTests:JobSchedulerServiceTest
Test: atest FrameworksMockingServicesTests:JobStatusTest
Test: atest FrameworksMockingServicesTests:QuotaControllerTest
Test: atest FrameworksServicesTests:JobStoreTest
Change-Id: I49738e44899ed4ceb37398b8875b6dabe387b205