BUG-2159: fix sort() conflict

Java 8 introduces a default method into java.util.List, which has a
different signature (and semantics) than the xtend extension. This patch
changes the code to not use the syntactic sugar while retaining the use
of the extension.

Change-Id: I4685937ab4da64cfe384db9aad31859ca51e97d7
Signed-off-by: Robert Varga <rovarga@cisco.com>
Merge "BUG-2159: fix sort() conflict"