Log EJ status to statsd.

Test output:
  data {
    elapsed_timestamp_nanos: 4320796331314
    atom {
      scheduled_job_state_changed {
        attribution_node {
          uid: 10483
          tag: ""
        }
        job_name: "android.jobscheduler.cts.jobtestapp/.TestJobService"
        state: SCHEDULED
        stop_reason: STOP_REASON_UNKNOWN
        standby_bucket: ACTIVE
        job_id: 4320
        has_charging_constraint: false
        has_battery_not_low_constraint: false
        has_storage_not_low_constraint: false
        has_timing_delay_constraint: false
        has_deadline_constraint: false
        has_idle_constraint: false
        has_connectivity_constraint: false
        has_content_trigger_constraint: false
        is_requested_expedited_job: true
        is_running_as_expedited_job: false
      }
    }
  }
  data {
    elapsed_timestamp_nanos: 4320802878606
    atom {
      scheduled_job_state_changed {
        attribution_node {
          uid: 10483
          tag: ""
        }
        job_name: "android.jobscheduler.cts.jobtestapp/.TestJobService"
        state: STARTED
        stop_reason: STOP_REASON_UNKNOWN
        standby_bucket: ACTIVE
        job_id: 4320
        has_charging_constraint: false
        has_battery_not_low_constraint: false
        has_storage_not_low_constraint: false
        has_timing_delay_constraint: false
        has_deadline_constraint: false
        has_idle_constraint: false
        has_connectivity_constraint: false
        has_content_trigger_constraint: false
        is_requested_expedited_job: true
        is_running_as_expedited_job: true
      }
    }
  }

Bug: 138239687
Bug: 171305774
Test: make statsd_testdrive && ./out/host/linux-x86/bin/statsd_testdrive 8
Change-Id: Ib395ab67a0cc1d4fadd5ff8772d94d6ba0f14503