Install dnf protected files only when policy is built
    
    If an user builds package with `%bcond mls 0` it ended with
        RPM build errors:
        error: Installed (but unpackaged) file(s) found:
           /etc/dnf/protected.d/selinux-policy-mls.conf
            Installed (but unpackaged) file(s) found:
           /etc/dnf/protected.d/selinux-policy-mls.conf
    
    With this change, dnf procted files for a policy is installed only when
    the policy is built.
    
    [skip changelog]