qemu_hotplug: Properly check for qemuMonitorDelDevice retval

Luckily, the function returns only 0 or -1 so all the checks work
as expected. Anyway, our rule is that a positive value means
success so if the function ever returns a positive value these
checks will fail. Make them check for a negative value properly.

At the same time fix qemuDomainDetachExtensionDevice() reval
check. It is somewhat related to the aim of this patch.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>

src/qemu/qemu_hotplug.c

@@ -5457,11 +5457,11 @@ int qemuDomainDetachControllerDevice(virQEMUDriverPtr driver,
 
     qemuDomainObjEnterMonitor(driver, vm);
     if (detach->type == VIR_DOMAIN_CONTROLLER_TYPE_PCI &&
-        qemuDomainDetachExtensionDevice(priv->mon, &detach->info)) {
+        qemuDomainDetachExtensionDevice(priv->mon, &detach->info) < 0) {
         goto exit_monitor;
     }
 
-    if (qemuMonitorDelDevice(priv->mon, detach->info.alias)) {
+    if (qemuMonitorDelDevice(priv->mon, detach->info.alias) < 0) {
         ignore_value(qemuDomainObjExitMonitor(driver, vm));
         goto cleanup;
     }
@@ -6975,7 +6975,7 @@ qemuDomainDetachInputDevice(virDomainObjPtr vm,
         qemuDomainMarkDeviceForRemoval(vm, &input->info);
 
     qemuDomainObjEnterMonitor(driver, vm);
-    if (qemuMonitorDelDevice(priv->mon, input->info.alias)) {
+    if (qemuMonitorDelDevice(priv->mon, input->info.alias) < 0) {
         ignore_value(qemuDomainObjExitMonitor(driver, vm));
         goto cleanup;
     }
@@ -7018,7 +7018,7 @@ qemuDomainDetachVsockDevice(virDomainObjPtr vm,
         qemuDomainMarkDeviceForRemoval(vm, &vsock->info);
 
     qemuDomainObjEnterMonitor(driver, vm);
-    if (qemuMonitorDelDevice(priv->mon, vsock->info.alias)) {
+    if (qemuMonitorDelDevice(priv->mon, vsock->info.alias) < 0) {
         ignore_value(qemuDomainObjExitMonitor(driver, vm));
         goto cleanup;
     }