make bootanalyze more robust

- handles adb hangup during boot up
  : can handle problematic devices better
- run kernel dmesg under separate thread and reduces
  chances for losing kernel log

Bug: 204450693
Test: ./system/extras/boottime_tools/bootanalyze/bootanalyze.py -c ./system/extras/boottime_tools/bootanalyze/config.yaml -r -n 10 -t -v

Change-Id: I7a467e9a85464e1caf82f718b21d4ca99adee745
1 file changed