Revert "Enable port tests to be run using gcc4.8"

This reverts commit 029ed106c5.

templates/tools/dockerfile/test/cxx_ubuntu1604_x64/Dockerfile.template

@@ -39,7 +39,7 @@
   # The clang-3.6 symlink for the default clang version was added
   # to Ubuntu 16.04 recently, so make sure it's installed.
   # Also install clang3.7.
-  RUN apt-get update && apt-get -y install gcc-4.8 gcc-4.8-multilib g++-4.8 g++-4.8-multilib clang-3.6 clang-3.7 && apt-get clean
+  RUN apt-get update && apt-get -y install clang-3.6 clang-3.7 && apt-get clean
   
   # Define the default command.
   CMD ["bash"]

tools/dockerfile/test/cxx_ubuntu1604_x64/Dockerfile

@@ -97,7 +97,7 @@ RUN mkdir /var/local/jenkins
 # The clang-3.6 symlink for the default clang version was added
 # to Ubuntu 16.04 recently, so make sure it's installed.
 # Also install clang3.7.
-RUN apt-get update && apt-get -y install gcc-4.8 gcc-4.8-multilib g++-4.8 g++-4.8-multilib clang-3.6 clang-3.7 && apt-get clean
+RUN apt-get update && apt-get -y install clang-3.6 clang-3.7 && apt-get clean
 
 # Define the default command.
 CMD ["bash"]