BUG-592: Fix InstanceIdentifier instantiation

This is a follow-up patch for
https://git.opendaylight.org/gerrit/#/c/5778 and gets rid of using
direct constructor use.

Change-Id: I09310b71c595a99bb09038f129b47b5b28aaaa33
Signed-off-by: Robert Varga <rovarga@cisco.com>
Signed-off-by: Tony Tkacik <ttkacik@cisco.com>
Merge "BUG-592: Fix InstanceIdentifier instantiation"