cros: Add check for |should_send_rlz_ping| in RW_VPD

Reading from VPD is supported by StatisticsProvider so IMO we can reuse
the code. There will be a follow-up Chrome OS CL to deal with writing
to VPD specifically.

Bug: 820783
Change-Id: I57de7212ca3b5366731789f0836ab5c6fcca294f
Reviewed-on: https://chromium-review.googlesource.com/969942
Commit-Queue: Wenzhao (Colin) Zang <[email protected]>
Reviewed-by: Alexander Alekseev <[email protected]>
Reviewed-by: Roger Tawa <[email protected]>
Cr-Commit-Position: refs/heads/master@{#545659}
14 files changed