qemu: hotplug: don't overwrite error message in qemuDomainAttachNetDevice

Since commit f14c37, virDomainConfVMNWFilterTeardown is reporting errors
thus any previously reported error gets overwritten.
We need to save the errors in qemuDomainAttachNetDevice before calling
this function when we are in cleanup code.

https://bugzilla.redhat.com/show_bug.cgi?id=1598311Signed-off-by: NKaterina Koukiou <kkoukiou@redhat.com>
Reviewed-by: NMichal Privoznik <mprivozn@redhat.com>

src/qemu/qemu_hotplug.c

@@ -793,6 +793,7 @@ qemuDomainAttachNetDevice(virQEMUDriverPtr driver,
     bool charDevPlugged = false;
     bool netdevPlugged = false;
     char *netdev_name;
+    virErrorPtr save_error = NULL;
 
     /* preallocate new slot for device */
     if (VIR_REALLOC_N(vm->def->nets, vm->def->nnets + 1) < 0)
@@ -1074,7 +1075,9 @@ qemuDomainAttachNetDevice(virQEMUDriverPtr driver,
             qemuDomainReleaseDeviceAddress(vm, &net->info, NULL);
 
         if (iface_connected) {
+            virErrorPreserveLast(&save_error);
             virDomainConfNWFilterTeardown(net);
+            virErrorRestore(&save_error);
 
             if (virDomainNetGetActualType(net) == VIR_DOMAIN_NET_TYPE_DIRECT) {
                 ignore_value(virNetDevMacVLanDeleteWithVPortProfile(