Ensure rbenv plugins directory exists for ruby-build

Author: bshand

lib/ndr_dev_support/capistrano/install_ruby.rb

@@ -71,6 +71,7 @@
                 cp -nvp #{latest_release}/vendor/rbenv/cache/* .rbenv/cache/;
               fi;
               if [ -f #{latest_release}/vendor/rbenv/ruby-build.tar.gz ]; then
+                mkdir -p .rbenv/plugins/;
                 tar xf #{latest_release}/vendor/rbenv/ruby-build.tar.gz -C .rbenv/plugins/ ruby-build;
               fi;
               eval \\"\\$(.rbenv/bin/rbenv init - --no-rehash bash)\\";