handle ADBTimeout in a debug message

[aerickson]

[task 2019-12-18T20:20:05.722Z] Traceback (most recent call last):
[task 2019-12-18T20:20:05.722Z]   File "/builds/taskcluster/script.py", line 250, in <module>
[task 2019-12-18T20:20:05.722Z]     sys.exit(main())
[task 2019-12-18T20:20:05.722Z]   File "/builds/taskcluster/script.py", line 227, in main
[task 2019-12-18T20:20:05.722Z]     enable_charging(device, device_type)
[task 2019-12-18T20:20:05.722Z]   File "/builds/taskcluster/script.py", line 58, in enable_charging
[task 2019-12-18T20:20:05.722Z]     print("script.py: enabling charging for device '%s' ('%s')..." % (device_type, device.get_info('id')['id']))
[task 2019-12-18T20:20:05.722Z]   File "/usr/local/lib/python3.6/dist-packages/mozdevice/adb.py", line 2883, in get_info
[task 2019-12-18T20:20:05.722Z]     info['id'] = self.command_output(['get-serialno'], timeout=timeout)
[task 2019-12-18T20:20:05.722Z]   File "/usr/local/lib/python3.6/dist-packages/mozdevice/adb.py", line 1215, in command_output
[task 2019-12-18T20:20:05.722Z]     timeout=timeout)
[task 2019-12-18T20:20:05.722Z]   File "/usr/local/lib/python3.6/dist-packages/mozdevice/adb.py", line 318, in command_output
[task 2019-12-18T20:20:05.722Z]     raise ADBTimeoutError("%s" % adb_process)
[task 2019-12-18T20:20:05.722Z] mozdevice.adb.ADBTimeoutError: args: adb wait-for-device get-serialno, exitcode: None, stdout: 

[bclary]

r+.

[aerickson]

Changed to handle ADBErrors the same as ADBTimeouts.

Diff since last review: fbca63e