Change docker TLS env file location

Move to a writable partition, and update for the fact
that we cannot `source` from noexec partition.

BUG=b:330123362

Change-Id: I37401ee5627eb864c336f1591f35258477a1301e
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/moblab/+/6067789
Auto-Submit: Michal Matyjek <[email protected]>
Tested-by: Michal Matyjek <[email protected]>
Commit-Queue: Jacek Klimkowicz <[email protected]>
Reviewed-by: Jacek Klimkowicz <[email protected]>
1 file changed