cros_choose_profile: do nothing if selected profile is the same

This lets us not worry about calling this script if the computed
path hasn't changed which simplifies calling code.

BUG=chromium-os:34519
TEST=running multiple times doesn't warn:
	cros_choose_profile --board stumpy --profile ''
TEST=running warns:
	cros_choose_profile --board stumpy --profile ''
	cros_choose_profile --board stumpy --profile 'kernel-next'

Change-Id: Ib052b4a6163a013739dea22abc30c32d3b4c4fc8
Reviewed-on: https://gerrit.chromium.org/gerrit/33483
Reviewed-by: Chris Sosa <sosa@chromium.org>
Commit-Ready: Mike Frysinger <vapier@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
1 file changed