Fix an issue that the icon rewritten logic not working in non-primary user

1.IconsContentProvider should be singleUser, i.e. it should run
  in user 0 only.
2.IconsContentProvider should get the icon from the calling user.

Fixes: 157073154

Test: Run our mts.
Test: Create a work profile. Select an email address, verify the icon.
Test: Create a work profile. Install a browser in work profile only.
      Select a URL and verify the icon
Change-Id: Idf4ef86f8f2aa110f755e9518cd151b943f2aea0