Bug 967118 - Make Platform/Cartridge shared files immutable

* Add OpenShift::ManagedFiles::IMMUTABLE_FILES
* Remove immutable files from all lock/unlock lists
* Refactor cartridge create to protect these files
Bug 967118 - Remove redundant entries from managed_files.yml

* Removed all occurances where locked_files was protecting just managed_files.yml
  and manifest.yml. Platform ensures those are immutable.
Merge pull request #2642 from jwhonce/bug/967118

Merged by openshift-bot