[autotest] Check existance of lsb-release file before testing chromite lib.

To check if the process is running in moblab, try to use lsb-release file
before testing if chromite lib call IsInsideChroot.
This is to avoid confusion of the error message "Unable to determine if this
is a moblab system"

BUG=None
TEST=local call lsbrelease_utils.is_moblab.

Change-Id: Ie1c325971e6947ef300770c33150987abbed5759
Reviewed-on: https://chromium-review.googlesource.com/263284
Trybot-Ready: Dan Shi <dshi@chromium.org>
Tested-by: Dan Shi <dshi@chromium.org>
Reviewed-by: Simran Basi <sbasi@chromium.org>
Commit-Queue: Dan Shi <dshi@chromium.org>
1 file changed