fastboot: reset timeout if INFO is received during long commands

As part of a refactor, commit db511207
added a timeout for receving responses for commands. Unfortunately,
the timeout is optimistic as to how quickly target devices can complete
such operations. Flash and erase commands can be quite slow on devices
with traditional flash chips. The fastboot protocol is already adept
at handling such cases because it allows for sending INFO packets during
these periods. We may receive one or more INFO packets during tehse long
operations. Every time we receive an INFO packet, it proves the remote
end is alive, but busy, which should reset our timeout timer.

Change-Id: Ia3bba21c497b22639b626d89711ecd4eb02504ed
Signed-off-by: Dima Zavin <dmitriyz@waymo.com>