BUG 1839 - HTTP delete of non existing data

Before - after deleting non existing data an exception was raised.
Now - after deleting non existing data it is checked whether there is in
exception chain instance of ModifiedNodeDoesNotExistException. If it is so then
HTTP 404 - data missing status is returned.

Change-Id: I43ccaa16abe7dfaffa3e031aa31d93f8f106a81f
Signed-off-by: Jozef Gloncak <jgloncak@cisco.com>
(cherry picked from commit 4c22825994c2519fb1c9d63f0050ebf35c4f8439)
Merge "BUG 1839 - HTTP delete of non existing data" into stable/helium