print out the contents of /tmp when we fail to create filesystem image

BUG=None
TEST=Ran platform_CrosDisksFilesystem on device

Change-Id: I3ddffd627c03217de222a91c818962e0ea9c9527
Reviewed-on: https://gerrit.chromium.org/gerrit/37728
Reviewed-by: Craig Harrison <craigdh@chromium.org>
Reviewed-by: Scott Zawalski <scottz@chromium.org>
Tested-by: Prashanth Balasubramanian <beeps@chromium.org>
Commit-Ready: Prashanth Balasubramanian <beeps@chromium.org>
1 file changed