Workaround for installing correct version of ruby bundler

See rubygems/bundler#6870

Bundler 2.x dropped support for Ruby < 2.3 so now we detect ruby
version and install last known to work version. This means that
newer OS will get newer versions of bundler.

Change-Id: I521affb16d8d2312be3ff507a014adddacd6cb8b
Closes-Bug: #1810401
(cherry picked from commit 6185377)

functions

@@ -24,6 +24,12 @@ install_gems() {
   sed -i "/.*ref[[:space:]]*=> 'stable\/.*/d" Gemfile
 
   # Install dependencies
-  gem install bundler --no-rdoc --no-ri --verbose
+  ruby <<EOF
+cmd = 'gem install bundler --no-rdoc --no-ri --verbose'
+if Gem::Version.new(RUBY_VERSION) < Gem::Version.new('2.3.0') then
+  cmd += ' -v 1.17.3'
+end
+system(cmd)
+EOF
   $GEM_HOME/bin/bundle install
 }