Update git submodules

* Update docs/submodules/releng-xci from branch 'master'
  - Merge "Bump sha on openstack-ansible-lxc_hosts"
  - Bump sha on openstack-ansible-lxc_hosts

    The commit 6b529de0315fe6cd12f6e78c00a5f2f2d3a01e28 in
    openstack-ansible-lxc_hosts reverts an earlier change that introduced
    systemd-networkd to lxc containers that run OpenStack services. This
    prevents the containers from being stopped (ie, lxc-stop fails until it
    times out), since systemd-networkd restarts. lxc-stop sends the SIGRT+3
    message to the container which the container interprets as "halt".
    systemd-networkd conflicts with shutdown, so when the system tries to
    enter halt, systemd-networkd gets started again. As a result, the
    container does not shut down cleanly.

    This patch uses a version of openstack-ansible-lxc_hosts that does not
    use systemd-networkd in the containers.

    Change-Id: Ie85d2117ce2e6e8afa87810d690eab78e3b3be3d
    Signed-off-by: Tapio Tallgren <tapio.tallgren@nokia.com>

diff --git a/docs/submodules/releng-xci b/docs/submodules/releng-xci
index 6503c6f..4b9f7b3 160000 (submodule)
--- a/docs/submodules/releng-xci
+++ b/docs/submodules/releng-xci
@@ -1 +1 @@
-Subproject commit 6503c6fbac486c38d7898656985c68d46b24ffe0
+Subproject commit 4b9f7b3f892486a8ea721aa72bed573db298fa69