cros: Use OAUTH_TOKEN_STATUS_UNKNOWN while loading token from db.

"Invalid" token status has side effect and causes issue 328920.
"Unknown" status works with 328920 and still sends user to Gaia
if loading from db fails for issue 328065.

BUG=328065,328920

Review URL: https://codereview.chromium.org/117443002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@241610 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 241610