Prevent waiting for NexusPlayers indefinitely

Prevent waiting for NexusPlayers indefinitely

Also, I noticed that sometimes the NexusPlayers would come back up such
that adb would recognize them, but not such that the sys.boot_completed
was set to 1.  This was usually fixed by rebooting the devices again.

This code will reboot them up to three times in total before giving
up and killing the device.

BUG=skia:
TBR=borenet,rmistry
NOTREECHECKS=true
NOTRY=true

Change-Id: Ic2217855ad643ab256a598a3f55a67ba84ebcb25
Reviewed-on: https://skia-review.googlesource.com/8285
Reviewed-by: Kevin Lubick <kjlubick@google.com>
Commit-Queue: Kevin Lubick <kjlubick@google.com>