Fix attaching files from shared with me on Drive.

Fix attaching files from shared with me on Drive.

If a user attaches a file from shared with me, then all consecutive tries to
attach will invoke Files app in a wrong state. Changing directories will be
impossible.

Shared files are under /other pseudo directory. However, in Files app we don't
support opening this directory. Instead we do a custom search on a fake entry.

If a file from shared with me is selected, then the location is remembered (at
/other), and the Files app tries to open /other when a select dialog is opened.

This patch resolves this issue by checking if the initial directory is /other.
If so, then opens the Drive main directory instead.

TEST=Tested manually with several scenarios.
BUG=416482

Review URL: https://codereview.chromium.org/637853002

Cr-Commit-Position: refs/heads/master@{#298686}