battery_mitigation: fix brownout reporting

Ensure ro.boot.bootreason equals sys.boot.reason before filing bugreport
for Brownout.

Bug: 263274350
Test: Local testing to confirm
Change-Id: I321a7c71bb7ef8c13fa49bb356be34bf789e7bef
Signed-off-by: George Lee <geolee@google.com>
3 files changed