[autotest] Add get_servo function to CrosHost class

Add a label detection function to CrosHost class.

BUG=chromium:349556
TEST=local test: ./atest host create 172.22.30.146
force servo_hostname to be a valid dut as a test.

Change-Id: Ia79198254195dca972f3669869d3456f71ae89b2
Reviewed-on: https://chromium-review.googlesource.com/191286
Reviewed-by: Dan Shi <dshi@chromium.org>
Commit-Queue: Dan Shi <dshi@chromium.org>
Tested-by: Dan Shi <dshi@chromium.org>
1 file changed