schema: Update memory information reported by the agent

Patch http://gerrit.ovirt.org/#/c/27156/ in the guest agent introduced
two new variables to be reported. This needs to be reflected in the API

Change-Id: I310a569f361371a25a35a7359525653dd6218317
Bug-Url: https://bugzilla.redhat.com/1024007
Signed-off-by: Vinzenz Feenstra <vfeenstr@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/27210
Reviewed-by: Amador Pahim <apahim@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>