Reduce VR NFC flakiness

Adds simNfcScanUntilVrEntered, which in most cases, replaces simNfcScan.
This is to deal with flakiness that stems from VrCore thinking that it's
still in VR from a previous test and nooping when it receives an NFC
scan in a following test.

Bug: 736527, 812306
Change-Id: If7b135b99df03c463f5b393bfbe6290e06d0ee4e
Reviewed-on: https://chromium-review.googlesource.com/923099
Reviewed-by: Michael Thiessen <mthiesse@chromium.org>
Commit-Queue: Brian Sheedy <bsheedy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#537342}
4 files changed