dumpxml: Add acl test cases for domain api read and read-secure

By default dumpxml with access to domain api 'read' will be
granted for unprivilidged user, add test cases testing this.

And for dumpxml with --security-info, add test cases with
domain api 'read-secure' in normal and error tests.

Signed-off-by: Wayne Sun <gsun@redhat.com>