fix the optional parameters error of api schema file

some discrptions of optional parameters miss #optional
some definitions of optional parameters miss *

Change-Id: Ia596c38bcb46aa0798ac2147376e9132be292750
Signed-off-by: ShaoHe Feng <shaohef@linux.vnet.ibm.com>
Reviewed-on: http://gerrit.ovirt.org/10447
Reviewed-by: Dan Kenigsberg <danken@redhat.com>