Description of problem:
When do docker build with ruby-20 images and https://github.com/openshift/ruby-hello-world.git repo, will meet below error:

Step 7 : RUN scl enable rh-ruby22 "bundle install"
 ---> Running in c609429a7aa7
Unable to open /etc/scl/conf/rh-ruby22!
F1223 03:39:39.148313       1 builder.go:70] Build error: The command '/bin/sh -c scl enable rh-ruby22 "bundle install"' returned a non-zero code: 1

Works for ruby-22 images

Version-Release number of selected component (if applicable):
openshift/ruby-20-rhel7  e69babf2d300
openshift3/ruby-20-rhel7 e4af9621f3fa

How reproducible:
always

Steps to Reproduce:
1.Create a dockerbuild app with ruby-20-rhel7 and ruby-hello-world repo.
 oc  new-app -f https://raw.githubusercontent.com/openshift-qe/v3-testfiles/master/build/ruby20rhel7-template-docker.json
2.Check build log
3.

Actual results:
2.Check build log
Step 7 : RUN scl enable rh-ruby22 "bundle install"
 ---> Running in c609429a7aa7
Unable to open /etc/scl/conf/rh-ruby22!
F1223 03:39:39.148313       1 builder.go:70] Build error: The command '/bin/sh -c scl enable rh-ruby22 "bundle install"' returned a non-zero code: 1

Expected results:
Could docker build

Additional info:
Should make this Dockerfile compatible with ruby-20 and ruby-22 images both.

https://github.com/openshift/ruby-hello-world/blob/master/Dockerfile
RUN scl enable rh-ruby22 "bundle install"
CMD ["scl", "enable", "rh-ruby22", "./run.sh"]