Update submodules: util (new commits)

util:
    c4dde2f Chris Smith <chris@dmdirc.com>
            Try to stop the downloader test flaking.

            Replace tempremental in-order mocking with a real output stream.
            Allow maps to be serialised in any order.

            Gerrit: http://gerrit.dmdirc.com/4066

Change-Id: I79a38f72cb083a453d0c55bd63cec24651f246ab