Bug 1781: Fix serialization of leafrefs

- fixed search leafref node specified with relative xpath

Change-Id: I4b6eb6ab94b954ab5b28129dc332590d32b8a7c4
Signed-off-by: Ladislav Borak <lborak@cisco.com>
Signed-off-by: Jozef Gloncak <jgloncak@cisco.com>
Merge "Bug 1781: Fix serialization of leafrefs"