Prevent possible ordering callback gaming.

Only use the enqueue time of jobs that would be ready with connectivity
so that apps can't try to schedule a job that would basically never run
in an effort to ensure they always get a callback registered for them.

Bug: 184740668
Test: atest frameworks/base/services/tests/servicestests/src/com/android/server/job
Test: atest frameworks/base/services/tests/mockingservicestests/src/com/android/server/job
Test: atest CtsJobSchedulerTestCases
Change-Id: I24cb8878bf04166e4ed7df3e6f5d1f8d06ad5f8b