dbus: Remove MockShillDeviceClient and MockShillIPConfigClient

These are not in use.
Along the way rename ShillDeviceClientStub to FakeShillDeviceClient
and ShillIPConfigClient to FakeShillIPConfigClient respectively.

BUG=234463,309506
TEST=none
R=hashimoto@chromium.org

Review URL: https://codereview.chromium.org/31513002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@229744 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 229744