Don't display multi-profile under Guest user.

Some settings make sense, even for Guest, but the profile management section should not be available.

BUG=285347

Review URL: https://codereview.chromium.org/167723002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@251861 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 251861