faft: Fix the wrong cros path when autotest not cros_workon'ed

Some tools of lab_test require the path of cros dir. We computed it
using the relative path of the current autotest dir. However, when
autotest is not cros_workon'ed, the run_remote_tests.sh script uses
the autotest code from /build/board/usr/local/autotest. The original
path-finding is wrong in this case. This CL is to change use the cros
dir from the environment variable CROS_WORKON_SRCROOT.

BUG=None
TEST=run the lab_test code without cros_workon'ed:
$ cros_workon-link stop autotest
$ run_remote_tests.sh --board link --remote dut RecoveryButton/control$

Change-Id: Ic1786c88bc295435a932b9a51711d9dc7ad7a293
Reviewed-on: https://gerrit.chromium.org/gerrit/37494
Reviewed-by: Mike Truty <truty@chromium.org>
Commit-Ready: Tom Wai-Hong Tam <waihong@chromium.org>
Tested-by: Tom Wai-Hong Tam <waihong@chromium.org>
1 file changed