Replace mariadb version in Dockerfile (#2980)

Error from apt:
Package libmariadbclient18 is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
However the following packages replace it:
  libmariadb3

Dockerfile

@@ -26,7 +26,7 @@ RUN groupadd -g 1000 forseti && \
 
 # Install host dependencies.
 RUN apt-get update  && \
-    apt-get install --no-install-recommends -y libmariadbclient18 && \
+    apt-get install --no-install-recommends -y libmariadb3 && \
     apt-get clean && \
     rm -rf /var/lib/apt/lists/*