Fix job persistence & re-inflation

We were persisting jobs' battery-not-low constraints but were not
properly restoring that constraint when the job was inflated at boot.
This could result in a runtime bootloop (!) if the job had no other
constraints, requiring a factory reset to restore the device to
usability.

We now:

* properly inflate the battery-not-low constraint;
* persist & inflate the storage-not-low constraint, which previously was
being stripped entirely and could result in a similar crash-at-boot;
* ignore the job rather than crash the system if one is inflated into
a non-viable state; and
* formally test previously-untested constraint persistence

Bug: 130012063
Test: atest $ANDROID_BUILD_TOP/frameworks/base/services/tests/servicestests/src/com/android/server/job/JobStoreTest.java
Test: atest CtsJobSchedulerTestCases
Test: JobStoreTest with forced throw in JobInfo.Builder#build()
Change-Id: Ia3ab1eb16aeaa85336409368b4340622cec19f4c