Add UpdateSharePath to SmbProviderClient

- Adds UpdateSharePath to SmbProviderClient.
- This function will interact with D-Bus to call on CrOS's
  smbprovider::UpdateSharePath.
- Update FakeSmbProviderClient to include UpdateSharePath.

Bug: chromium:922273
Test: Compiles
Change-Id: I7d70c1578293a9d29f229590eb15777970197414
Reviewed-on: https://chromium-review.googlesource.com/c/1445231
Commit-Queue: jimmy gong <jimmyxgong@chromium.org>
Reviewed-by: Zentaro Kavanagh <zentaro@chromium.org>
Reviewed-by: Bailey Berro <baileyberro@chromium.org>
Cr-Commit-Position: refs/heads/master@{#629695}
4 files changed