restapi : RSDL lists host display address as mandatory(#915066)

Host display address is listed as a mandatory parameter in api?rsdl

This patch changes the host.display.address to optional parameter

Change-Id: Iaa6d7799d9e8f2bf45e8bb076c40afafff9f5e07
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=915066
Signed-off-by: Ravi Nori <rnori@redhat.com>