This PR fixes two issues:

1. Panic on nil pushInfo when pushing more than one deviceInfo (inside the pushConcurrent), and fixes it by not pushing a job if the pushInfo is nil.
2. The check logic was flipped to determine how many workers to spawn, rendering the preset worker boundary useless, if more pushInfo came through, it would spawn X amount of workers, now it caps at the workers boundary, or downsizes if less than that.