Signed-off-by: bacrossland bryan.crossland@target.com

Why I did it

Fix updated sonic-swss submodule which uses GMock for testing:

    08711a8 [orchdaemon]: Fixed sairedis record file rotation (sonic-net#2481)

How I did it

Add install of GMock to Dockerfile.j2 in all Debian releases.

sonic-slave-stretch/Dockerfile.j2

@@ -384,7 +384,7 @@ RUN apt-get install -y vim
 # Install rsyslog
 RUN apt-get install -y rsyslog
 
-RUN apt-get install -y libgtest-dev
+RUN apt-get install -y libgtest-dev -t stretch-backports
 
 # For gmock
 RUN apt-get install -y libgmock-dev -t stretch-backports