dragon: Exclude invalid/non-updatable firmwares from keyboard update service

This CL adds the logic to catch the version number parsing exception caused by
previous distribution of dev-signed keyboard firmware. This CL also adds the
minimum updatable firmware version(0.151020) to exclude the non-updatable
Pixel C keyboard.

Bag: 25831957
TEST=build and run Pixel C Keyboard Firmware Updater service

Change-Id: I74eaac4832a2c44d7552c0e5e13bc77694152666
2 files changed