Merge branch 'stable-4.11' into stable-5.0

* stable-4.11:
  Fix NoSuchFileException during directory cleanup in RefDirectory
  Externalize warning message in RefDirectory.delete()
  Suppress warning for trying to delete non-empty directory

Change-Id: Ic7eaa0b6a4e750bc7853eb549a9e126269ae22cf
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

diff --cc org.eclipse.jgit/resources/org/eclipse/jgit/internal/JGitText.properties
Simple merge

diff --cc org.eclipse.jgit/src/org/eclipse/jgit/internal/JGitText.java
Simple merge

diff --cc org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/RefDirectory.java
Simple merge