upgrade gerrit to 2.16.8

Change-Id: I8c86dbe0bbe6e75e405269299d65d128112833da

gerrit/Dockerfile

@@ -28,7 +28,7 @@ RUN apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 1871F775 && \
     apt-key update && \
     apt-get -y install openssh-client sudo && \
     apt-get -y install openjdk-8-jdk && \
-    apt-get -y install gerrit=2.16.7-1 && \
+    apt-get -y install gerrit=2.16.8-1 && \
     rm -f /var/gerrit/logs/* && \
     rm -rf /var/lib/apt/lists/*