Fix gate by adding MariaDB-shared dependnecy

With the reorganization of the MariaDB repository, the C libraries
for mariadb were not included in the toolbox container.  This results
in a non-functional CentOS environment which is resolved by this
simple patch.

Change-Id: Ib4a2f7e55b6efc36bc3ff2d93447cb97b7b109f5
Closes-Bug: #1561347

docker/kolla-toolbox/Dockerfile.j2

@@ -10,6 +10,7 @@ RUN yum -y install \
         libxml2-devel \
         libxslt-devel \
         MariaDB-devel \
+        MariaDB-shared \
         openssl-devel \
         python-devel \
         openssh-clients \