BootReceiver: Report correct headers for last messages

BootReceiver was using current build information when reporting
various versions. This was causing A/B devices to report the
wrong build information when reporting crashes since rebooting
a A/B device with a pending OTA would automatically apply the
OTA. (the problem was not seen on devices without A/B due to
booting through recovery to apply the OTA)

Bug: 30594862
Change-Id: I6f52081142e338c822c9135cba48a1f88f4d4bdb