Chameleon: Support label with connection

This change improves the Chameleon label with the display connection.
For example, for the DUTs connected with Chameleon via HDMI, label them
'chameleon:hdmi'.

BUG=chromium:394436
TEST=Manual
To test that the label is assigned correctly, modified the contol file
of display_Resolution.mirrored:

    def run(machine):
        host = hosts.create_host(machine, chameleon_args=chameleon_args)
        labels = host.get_labels()
        print '\n\n\nXXX\n'
        print labels

Ran the test display_Resolution.mirrored and checked the new label.

Change-Id: Icef5338f06924d2eaf9371fc43f2b8e5f4986f46
Reviewed-on: https://chromium-review.googlesource.com/211925
Reviewed-by: Wai-Hong Tam <waihong@chromium.org>
Commit-Queue: Wai-Hong Tam <waihong@chromium.org>
Tested-by: Wai-Hong Tam <waihong@chromium.org>
2 files changed