Allow to pass remount option to Mount method of cros_disks.
The remount option will be handled by cros_disks after this change:
https://chromium-review.googlesource.com/#/c/390410/

BUG=642247

Review-Url: https://chromiumcodereview.appspot.com/2392503002
Cr-Commit-Position: refs/heads/master@{#426792}
6 files changed