Close all sockets before cancelling QEMU migration

Cancelling the QEMU migration may cause QEMU to flush pending
data on the migration socket. This may in turn block QEMU if
nothing reads from the other end of the socket. Closing the
socket before cancelling QEMU migration avoids this possible
deadlock.

* src/qemu/qemu_migration.c: Close sockets before cancelling
  migration on failure

src/qemu/qemu_migration.c

@@ -1494,6 +1494,8 @@ static int doTunnelMigrate(struct qemud_driver *driver,
 
 cancel:
     if (ret != 0 && virDomainObjIsActive(vm)) {
+        VIR_FORCE_CLOSE(client_sock);
+        VIR_FORCE_CLOSE(qemu_sock);
         qemuDomainObjEnterMonitorWithDriver(driver, vm);
         qemuMonitorMigrateCancel(priv->mon);
         qemuDomainObjExitMonitorWithDriver(driver, vm);