Fix job enqueue bug when changing constraints

If a job with pending work had new work enqueued but with a changed set
of constraints (including temporal constraints), the system was
accidentally discarding the new work item, leaving only the
previously-pending ones.  Now that's fixed:  changing constraints works as
expected, changing the execution criteria for the job, retaining all
pending work, and adding the new work to the end of the queue.

Bug: 141707520
Test: atest CtsJobSchedulerSharedUidTestCases:EnqueueJobWorkTest#testEnqueuedWorkNewConstraints
Change-Id: I92e42049937847922f1fa9a10432ec87676408d0