api: Convert process_schema.py to use vdsmapi.get_api()

Change-Id: Id4f6ec96f503b41fc1c976f515feb15a58a33747
Signed-off-by: Adam Litke <agl@us.ibm.com>
Reviewed-on: http://gerrit.ovirt.org/12109
Reviewed-by: Dan Kenigsberg <danken@redhat.com>
Tested-by: Dan Kenigsberg <danken@redhat.com>