Optimistically assume the parent folder already exists on local File
System when it exists in workspace. So do not explicitly check it. If it
did not exist file write will fail and can be retried after creating the
parent in File System - which can only happen when the workspace is out
of sync with local File System.
This optimization is only implemented for byte[] content in the not
appending case:

 * InputStream content would need a reset.
 * In append mode it is not obvious if something was already appended.

https://github.com/eclipse-platform/eclipse.platform/issues/1443