use RubyGems version in base docker image

Change-Id: I740ac57029983f82a7d8508a3798b47b93c3fa88
Reviewed-on: https://gerrit.instructure.com/140249
Tested-by: Jenkins
Reviewed-by: Marc Alan Phillips <mphillips@instructure.com>
QA-Review: Tyler Burraston <tburraston@instructure.com>
Product-Review: Bryan Petty <bpetty@instructure.com>

Dockerfile

@@ -40,7 +40,6 @@ RUN curl -sL https://deb.nodesource.com/setup_8.x | bash - \
 RUN if [ -e /var/lib/gems/$RUBY_MAJOR.0/gems/bundler-* ]; then BUNDLER_INSTALL="-i /var/lib/gems/$RUBY_MAJOR.0"; fi \
   && gem uninstall --all --ignore-dependencies --force $BUNDLER_INSTALL bundler \
   && gem install bundler --no-document -v 1.15.2 \
-  && gem update --system --no-document \
   && find $GEM_HOME ! -user docker | xargs chown docker:docker
 
 # We will need sfnt2woff in order to build fonts

Dockerfile-production

@@ -35,7 +35,6 @@ RUN curl -sL https://deb.nodesource.com/setup_8.x | bash - \
 RUN if [ -e /var/lib/gems/$RUBY_MAJOR.0/gems/bundler-* ]; then BUNDLER_INSTALL="-i /var/lib/gems/$RUBY_MAJOR.0"; fi \
   && gem uninstall --all --ignore-dependencies --force $BUNDLER_INSTALL bundler \
   && gem install bundler --no-document -v 1.15.2 \
-  && gem update --system --no-document \
   && find $GEM_HOME ! -user docker | xargs chown docker:docker
 
 

build/Dockerfile.template

@@ -41,7 +41,6 @@ RUN curl -sL https://deb.nodesource.com/setup_8.x | bash - \
 RUN if [ -e /var/lib/gems/$RUBY_MAJOR.0/gems/bundler-* ]; then BUNDLER_INSTALL="-i /var/lib/gems/$RUBY_MAJOR.0"; fi \
   && gem uninstall --all --ignore-dependencies --force $BUNDLER_INSTALL bundler \
   && gem install bundler --no-document -v 1.15.2 \
-  && gem update --system --no-document \
   && find $GEM_HOME ! -user docker | xargs chown docker:docker
 
 <% if development? -%>