Use Ubuntu 14.04.5 in Docker build

BUG=
TEST=compile
REF_BUG=
REF_CL=
REF_TIME=
REF_TIME_RAW=

Author: yukawa

docker/ubuntu14.04/Dockerfile

@@ -27,7 +27,7 @@
 # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-FROM ubuntu:14.04.2
+FROM ubuntu:14.04.5
 
 ENV DEBIAN_FRONTEND noninteractive