In commit 76b9aba2 I tried to refactor qemuDomainStorageSourceAccessAllow
but used wrong operators for adding bitwise flags.

This way the flags would result in 0 if any of them would be applied.
Signed-off-by: NPeter Krempa <pkrempa@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>