qemuDomainAttachNetDevice: Avoid @originalError leak

Coverity identified that this variable might be leaked. And it's
right. If an error occurred and we have to roll back the control
jumps to try_remove label where we save the current error (see
0e82fa4c for more info). However, inside the code a jump onto
other label is possible thus leaking the error object.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>

src/qemu/qemu_hotplug.c

@@ -1326,8 +1326,7 @@ qemuDomainAttachNetDevice(virQEMUDriverPtr driver,
     if (vlan < 0) {
         if (virQEMUCapsGet(priv->qemuCaps, QEMU_CAPS_NETDEV)) {
             char *netdev_name;
-            if (virAsprintf(&netdev_name, "host%s", net->info.alias) < 0)
-                goto cleanup;
+            if (virAsprintf(&netdev_name, "host%s", net->info.alias) >= 0) {
                 qemuDomainObjEnterMonitor(driver, vm);
                 if (charDevPlugged &&
                     qemuMonitorDetachCharDev(priv->mon, charDevAlias) < 0)
@@ -1338,13 +1337,13 @@ qemuDomainAttachNetDevice(virQEMUDriverPtr driver,
                              netdev_name);
                 ignore_value(qemuDomainObjExitMonitor(driver, vm));
                 VIR_FREE(netdev_name);
+            }
         } else {
             VIR_WARN("Unable to remove network backend");
         }
     } else {
         char *hostnet_name;
-        if (virAsprintf(&hostnet_name, "host%s", net->info.alias) < 0)
-            goto cleanup;
+        if (virAsprintf(&hostnet_name, "host%s", net->info.alias) >= 0) {
             qemuDomainObjEnterMonitor(driver, vm);
             if (hostPlugged &&
                 qemuMonitorRemoveHostNetwork(priv->mon, vlan, hostnet_name) < 0)
@@ -1353,6 +1352,7 @@ qemuDomainAttachNetDevice(virQEMUDriverPtr driver,
             ignore_value(qemuDomainObjExitMonitor(driver, vm));
             VIR_FREE(hostnet_name);
         }
+    }
     virSetError(originalError);
     virFreeError(originalError);
     goto cleanup;