Device locking

[mchack-work]

Investigate device locking in different operating system.

Trying to run two tkey-runapp at once messes up the firmware but doesn't enter failed state. This works for me as an ordinary non-root user. If the serial package doesn't support device locking we should implement it ourselves somehow on the client side.

Might also need to look into why the firmware isn't in state failed.

% ./tkey-runapp apps/signer/app.bin &; ./tkey-runapp apps/signer/app.bin
[1] 91914
Auto-detected serial port /dev/ttyACM0
Connecting to device on serial port /dev/ttyACM0 ...
Auto-detected serial port /dev/ttyACM0
Connecting to device on serial port /dev/ttyACM0 ...
GetNameVersion failed: ReadFrame: Expected cmdlen 2 (32 bytes), got 1 (4 bytes)
If the serial port is correct, then the TKey might not be in firmware-
mode, and have an app running already. Please unplug and plug it in again.
[1]  + exit 1     ./tkey-runapp apps/signer/app.bin
Firmware name0:'tk m' name1:'kdf' version:0
GetUDI failed: ReadFrame: Message not meant for us: dest 0