Add missing call to re-attach host devices if VM startup fails

If there is a problem with VM startup, PCI devices may be left
assigned to pci-stub / pci-back. Adding a call to reattach
host devices in the cleanup path is required.

* qemu/qemu_driver.c: qemuDomainReAttachHostDevices() when
  VM startup fails

src/qemu/qemu_driver.c

@@ -2749,6 +2749,8 @@ cleanup:
     /* We jump here if we failed to start the VM for any reason
      * XXX investigate if we can kill this block and safely call
      * qemudShutdownVMDaemon even though no PID is running */
+    qemuDomainReAttachHostDevices(conn, driver, vm->def);
+
     if (driver->securityDriver &&
         driver->securityDriver->domainRestoreSecurityAllLabel)
         driver->securityDriver->domainRestoreSecurityAllLabel(conn, vm);