qemu: driver: Unset log file watcher after restoring a VM save file

qemuProcessStart does not unset the infrastructure that retrieves errors
from the qemu log file in case of migration. As this wasn't handled
properly in qemuDomainSaveImageStartVM we kept the logging context/fd
open for the lifetime of the VM rather than closing it after it's not
needed.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1325080

src/qemu/qemu_driver.c

@@ -6523,6 +6523,11 @@ qemuDomainSaveImageStartVM(virConnectPtr conn,
     if (!restored)
         goto cleanup;
 
+    /* qemuProcessStart doesn't unset the qemu error reporting infrastructure
+     * in case of migration (which is used in this case) so we need to reset it
+     * so that the handle to virtlogd is not held open unnecessarily */
+    qemuMonitorSetDomainLog(qemuDomainGetMonitor(vm), NULL, NULL, NULL);
+
     event = virDomainEventLifecycleNewFromObj(vm,
                                      VIR_DOMAIN_EVENT_STARTED,
                                      VIR_DOMAIN_EVENT_STARTED_RESTORED);