conf: Extract update of vcpu count if maxvcpus is decreased

The code can be unified into the new accessor rather than being
scattered accross the drivers.

src/conf/domain_conf.c

@@ -1288,6 +1288,9 @@ int
 virDomainDefSetVcpusMax(virDomainDefPtr def,
                         unsigned int maxvcpus)
 {
+    if (maxvcpus < def->vcpus)
+        def->vcpus = maxvcpus;
+
     def->maxvcpus = maxvcpus;
 
     return 0;

src/libxl/libxl_driver.c

@@ -2188,9 +2188,6 @@ libxlDomainSetVcpusFlags(virDomainPtr dom, unsigned int nvcpus,
     case VIR_DOMAIN_VCPU_MAXIMUM | VIR_DOMAIN_VCPU_CONFIG:
         if (virDomainDefSetVcpusMax(def, nvcpus) < 0)
             goto cleanup;
-
-        if (nvcpus < def->vcpus)
-            def->vcpus = nvcpus;
         break;
 
     case VIR_DOMAIN_VCPU_CONFIG:

src/qemu/qemu_driver.c

@@ -4981,9 +4981,6 @@ qemuDomainSetVcpusFlags(virDomainPtr dom, unsigned int nvcpus,
             if (flags & VIR_DOMAIN_VCPU_MAXIMUM) {
                 if (virDomainDefSetVcpusMax(persistentDef, nvcpus) < 0)
                     goto endjob;
-
-                if (nvcpus < persistentDef->vcpus)
-                    persistentDef->vcpus = nvcpus;
             } else {
                 persistentDef->vcpus = nvcpus;
             }

src/test/test_driver.c

@@ -2379,9 +2379,6 @@ testDomainSetVcpusFlags(virDomainPtr domain, unsigned int nrCpus,
         if (flags & VIR_DOMAIN_VCPU_MAXIMUM) {
             if (virDomainDefSetVcpusMax(persistentDef, nrCpus) < 0)
                 goto cleanup;
-
-            if (nrCpus < persistentDef->vcpus)
-                persistentDef->vcpus = nrCpus;
         } else {
             persistentDef->vcpus = nrCpus;
         }

src/xen/xm_internal.c

@@ -706,9 +706,6 @@ xenXMDomainSetVcpusFlags(virConnectPtr conn,
     if (flags & VIR_DOMAIN_VCPU_MAXIMUM) {
         if (virDomainDefSetVcpusMax(entry->def, vcpus) < 0)
             goto cleanup;
-
-        if (entry->def->vcpus > vcpus)
-            entry->def->vcpus = vcpus;
     } else {
         entry->def->vcpus = vcpus;
     }