Only add new crostini shared path to prefs if it does not already exist.

Bug: 878324
Change-Id: I2d738bb3f980d200b946f0b6cf7522b830f4d5ac
Reviewed-on: https://chromium-review.googlesource.com/c/1334669
Reviewed-by: Nicholas Verne <nverne@chromium.org>
Commit-Queue: Joel Hockey <joelhockey@chromium.org>
Cr-Commit-Position: refs/heads/master@{#607908}
2 files changed