If unwrap returns null, we need to fall through to load to try it again.
(cherry picked from commit 04c87d8d)

Ensure that SortedList clones the underlying data list.
Without this changes to a clone also change the original list.
(cherry picked from commit 761c4379)

Ensure that SortedList clones the underlying data list.
Without this changes to a clone also change the original list.

Added uninstaller that removes *.jpi.

Thanks to newenigma for catching.

[FIXED JENKINS-14667] JDK installation failed on some slaves with InvalidClassException: hudson.tools.JDKInstaller$Platform$1; local class incompatible: …

From what I was told by Emanuele today in the office hours, this came up
during the Copenhagen hackathon.