Chameleon: Change the logic of resetting Chameleon board

The reset method of Chameleon is now to restore the EDID to a default one.
Change a bit of the test logic such that it does not waste time for
unnecessary EDID changes.

BUG=chromium:345540
TEST=test_that --arg="chameleon_host=$CHAMELEON" $DUT e:display_Resolution.*

Change-Id: If33d3130c88f3d24d343101b48d637aab70bfda3
Reviewed-on: https://chromium-review.googlesource.com/188712
Reviewed-by: Hung-ying Tyan <tyanh@chromium.org>
Commit-Queue: Wai-Hong Tam <waihong@chromium.org>
Tested-by: Wai-Hong Tam <waihong@chromium.org>
2 files changed