Listening on root with multiple shards is not tested anywhere,
add some test coverage.
JIRA: CONTROLLER-1932
Change-Id: Ie0d94f2d9b90869a140b73d85f1696df712fad25 Signed-off-by: Tibor Král <tibor.kral@pantheon.tech> Signed-off-by: Robert Varga <robert.varga@pantheon.tech>