make selinux permissive

selinux policy conflicts with kubernetes volumes
default number_of_minions to 1
If statement should pass if IMAGE exists

The if statement should pass when IMAGE exists
and if not revert to the default value.
Merge pull request #7 from rthallisey/master

If statement should pass if IMAGE exists
corrections to get-image.sh script

- fixed an order-of-operations issue that could have resulted in
  conflicts between docker-io and legacy "docker" package
- customize a copy of downloaded image rather than the original (to make
  it easier to start from scratch)
- make sure to clean up yum cache