[IOT-1906] Disable only /oic/res response under OCStopMulticastServer.

[IOT-1906] Disable only /oic/res response under OCStopMulticastServer.

The intent of this API is to stop responding to /oic/res responses
when resources are registered with a resource directory.  Stopping all
multicast reception prevents ownership transfer from working.

Bug: https://jira.iotivity.org/browse/IOT-1906
Change-Id: I01e183b6f5a249a4d0e32baf14f542774a3ca0cb
Signed-off-by: Todd Malsbary <todd.malsbary@intel.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/17633
Tested-by: jenkins-iotivity <jenkins@iotivity.org>
Reviewed-by: Dan Mihai <Daniel.Mihai@microsoft.com>