CLOUDSTACK-10220: Configure IPv4 alias on VR regardless of IPv6 (#2396)

IPv4 and IPv6 are two different protocols and the presence of IPv6
in a network does not mean that IPv4 aliases/multiple subnets should
not be configured or supported by the VR.

This if-statement was written almost 5 years ago in a attempt to
add IPv6 support to CloudStack but was never fully implemented.

Signed-off-by: Wido den Hollander <wido@widodh.nl>

Author: wido

engine/orchestration/src/org/apache/cloudstack/engine/orchestration/NetworkOrchestrator.java

@@ -1306,9 +1306,7 @@ protected boolean prepareElement(final NetworkElement element, final Network net
             if (_networkModel.areServicesSupportedInNetwork(network.getId(), Service.Dhcp)
                     && _networkModel.isProviderSupportServiceInNetwork(network.getId(), Service.Dhcp, element.getProvider()) && element instanceof DhcpServiceProvider) {
                 final DhcpServiceProvider sp = (DhcpServiceProvider)element;
-                final Map<Capability, String> dhcpCapabilities = element.getCapabilities().get(Service.Dhcp);
-                final String supportsMultipleSubnets = dhcpCapabilities.get(Capability.DhcpAccrossMultipleSubnets);
-                if (supportsMultipleSubnets != null && Boolean.valueOf(supportsMultipleSubnets) && profile.getIPv6Address() == null) {
+                if (isDhcpAccrossMultipleSubnetsSupported(sp)) {
                     if (!sp.configDhcpSupportForSubnet(network, profile, vmProfile, dest, context)) {
                         return false;
                     }