Adding force_flash functionality

aosp/2452605 might've accidentally omitted force flash functionality
from fastboot. Some users need to flash dynamic partitions from
bootloader, so we are readding this feature back into fastboot

Test: adb reboot bootloader, fastboot flash system --force

Change-Id: I37a51ebbe38b27ed428c38068d30c0febd7db09c
1 file changed