Store -1 directly for unlimited NIC network rate instead of NULL

nics.network_rate was unsigned, so the only way to represent "unlimited"
was NULL, even though every response-building call site already
normalizes null/non-positive to -1 for API output - meaning NULL and -1
were already behaviorally equivalent, just inconsistent at the storage
layer. NetworkModelImpl.getNetworkRate() never actually returns null
(always a positive rate or -1), so the null-coalescing in
NetworkOrchestrator was dead code once the column can hold -1 directly.

Make the column signed so it can store -1 like every other "resolved"
rate value in the codebase, simplify both NetworkOrchestrator call
sites to store the value as-is, and let the backfill persist -1 for
NICs whose legacy rate is unlimited instead of leaving them NULL.

Author: sudo87

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

@@ -1233,7 +1233,7 @@ public Pair<NicProfile, Integer> allocateNic(final NicProfile requested, final N
         NicVO vo = checkForRaceAndAllocateNic(requested, network, isDefaultNic, deviceId, vm);
 
         final Integer networkRate = _networkModel.getNetworkRate(network.getId(), vm.getId());
-        vo.setNetworkRate(networkRate != null && networkRate > 0 ? networkRate : null);
+        vo.setNetworkRate(networkRate);
         final NicProfile vmNic = new NicProfile(vo, network, vo.getBroadcastUri(), vo.getIsolationUri(), networkRate, _networkModel.isSecurityGroupSupportedInNetwork(network),
                 _networkModel.getNetworkTag(vm.getHypervisorType(), network));
         if (vm.getType() == Type.DomainRouter) {
@@ -2307,7 +2307,7 @@ public NicProfile prepareNic(final VirtualMachineProfile vmProfile, final Deploy
             nic.setState(Nic.State.Reserved);
         }
 
-        nic.setNetworkRate(networkRate != null && networkRate > 0 ? networkRate : null);
+        nic.setNetworkRate(networkRate);
 
         if (vmProfile.getType() == Type.DomainRouter) {
             Pair<NetworkVO, VpcVO> networks = getGuestNetworkRouterAndVpcDetails(vmProfile.getId());

engine/schema/src/main/java/com/cloud/upgrade/NetworkRateBackfill.java

@@ -90,7 +90,7 @@ private void backfillNicNetworkRates() {
                 final boolean defaultNic = rs.getBoolean("default_nic");
                 try {
                     final Integer rate = computeLegacyNicNetworkRate(networkId, instanceId, defaultNic);
-                    if (rate != null && rate > 0) {
+                    if (rate != null && rate != 0) {
                         updateNicNetworkRate(nicId, rate);
                     }
                 } catch (Exception e) {

engine/schema/src/main/resources/META-INF/db/schema-42300to2400.sql

@@ -19,6 +19,6 @@
 -- Schema upgrade from 4.23.0.0 to 24.0.0
 --;
 
-ALTER TABLE `cloud`.`nics` ADD COLUMN `network_rate` int unsigned DEFAULT NULL COMMENT 'effective network rate in Mb/s for this NIC';
+ALTER TABLE `cloud`.`nics` ADD COLUMN `network_rate` int DEFAULT NULL COMMENT 'effective network rate in Mb/s for this NIC, -1 means unlimited';
 
 ALTER TABLE `cloud`.`vpc_offerings` ADD COLUMN `public_nw_rate` smallint unsigned DEFAULT NULL COMMENT 'public gateway (internet-facing) network rate throttle mbits/s';