conf: Don't report errors from virDomainDefGetVcpu

Most callers make sure that it's never called with an out of range vCPU.
Every other caller reports a different error explicitly. Drop the error
reporting and clean up some dead code paths.

src/conf/domain_conf.c

@@ -1427,12 +1427,8 @@ virDomainVcpuDefPtr
 virDomainDefGetVcpu(virDomainDefPtr def,
                     unsigned int vcpu)
 {
-    if (vcpu >= def->maxvcpus) {
-        virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
-                       _("vCPU '%u' is not present in domain definition"),
-                       vcpu);
+    if (vcpu >= def->maxvcpus)
         return NULL;
-    }
 
     return &def->vcpus[vcpu];
 }

src/qemu/qemu_driver.c

@@ -4606,14 +4606,11 @@ qemuDomainHotplugAddVcpu(virQEMUDriverPtr driver,
                          unsigned int vcpu)
 {
     qemuDomainObjPrivatePtr priv = vm->privateData;
-    virDomainVcpuDefPtr vcpuinfo;
+    virDomainVcpuDefPtr vcpuinfo = virDomainDefGetVcpu(vm->def, vcpu);
     int ret = -1;
     int rc;
     int oldvcpus = virDomainDefGetVcpus(vm->def);
 
-    if (!(vcpuinfo = virDomainDefGetVcpu(vm->def, vcpu)))
-        return -1;
-
     if (vcpuinfo->online) {
         virReportError(VIR_ERR_INVALID_ARG,
                        _("vCPU '%u' is already online"), vcpu);
@@ -4658,14 +4655,11 @@ qemuDomainHotplugDelVcpu(virQEMUDriverPtr driver,
                          unsigned int vcpu)
 {
     qemuDomainObjPrivatePtr priv = vm->privateData;
-    virDomainVcpuDefPtr vcpuinfo;
+    virDomainVcpuDefPtr vcpuinfo = virDomainDefGetVcpu(vm->def, vcpu);
     int ret = -1;
     int rc;
     int oldvcpus = virDomainDefGetVcpus(vm->def);
 
-    if (!(vcpuinfo = virDomainDefGetVcpu(vm->def, vcpu)))
-        return -1;
-
     if (!vcpuinfo->online) {
         virReportError(VIR_ERR_INVALID_ARG,
                        _("vCPU '%u' is already offline"), vcpu);