Add spaces around operators.

Signed-off-by: Zhang Han <zhanghan64@huawei.com>
Message-Id: <20201228071129.24563-4-zhanghan64@huawei.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>