Patch sets for usb hotplug function

1) libvirt_bench: Add stress tests for usb-device hotplug function.
2) libvirt: add tests for controller involving usb-device hotplug.
3) libvirt: add tests for usb-device hotplug function
    The test target device includes keyboard, mouse, tablet, and disk.
@yangdongsheng 
Thank you for your help and i have accepted your suggestion.
and extending the timeout to 160s.
The test result is below,

Note: maybe you will curious about the time stamp "run-2014-12-27-04.50.33"
          It‘s just only a problem with time setting on test server.
          so please do not  mind it.


[root@RX300S6-2 virt]# ./run -t libvirt --no-downloads -k --keep-image-between-tests  --tests "type_specific.io-github-autotest-libvirt.libvirt_usb_hotplug_bench"
SETUP: PASS (0.20 s)
DATA DIR: /iso/shaosa
DEBUG LOG: /home/autotest_fjtest_release/client/tests/virt/logs/run-2014-12-27-04.50.33/debug.log
TESTS: 15
(1/15) type_specific.io-github-autotest-libvirt.libvirt_usb_hotplug_bench.no_bench.qemu_monitor.keyboard: PASS (137.54 s)
(2/15) type_specific.io-github-autotest-libvirt.libvirt_usb_hotplug_bench.no_bench.qemu_monitor.mouse: PASS (136.41 s)
(3/15) type_specific.io-github-autotest-libvirt.libvirt_usb_hotplug_bench.no_bench.qemu_monitor.tablet: PASS (135.37 s)
(4/15) type_specific.io-github-autotest-libvirt.libvirt_usb_hotplug_bench.no_bench.qemu_monitor.disk: PASS (227.22 s)
(5/15) type_specific.io-github-autotest-libvirt.libvirt_usb_hotplug_bench.no_bench.attach_device.disk: PASS (339.04 s)
(6/15) type_specific.io-github-autotest-libvirt.libvirt_usb_hotplug_bench.iozone.qemu_monitor.keyboard: PASS (171.90 s)
(7/15) type_specific.io-github-autotest-libvirt.libvirt_usb_hotplug_bench.iozone.qemu_monitor.mouse: PASS (163.72 s)
(8/15) type_specific.io-github-autotest-libvirt.libvirt_usb_hotplug_bench.iozone.qemu_monitor.tablet: PASS (166.93 s)
(9/15) type_specific.io-github-autotest-libvirt.libvirt_usb_hotplug_bench.iozone.qemu_monitor.disk: PASS (377.01 s)
(10/15) type_specific.io-github-autotest-libvirt.libvirt_usb_hotplug_bench.iozone.attach_device.disk: PASS (729.77 s)
(11/15) type_specific.io-github-autotest-libvirt.libvirt_usb_hotplug_bench.stress.qemu_monitor.keyboard: PASS (182.25 s)
(12/15) type_specific.io-github-autotest-libvirt.libvirt_usb_hotplug_bench.stress.qemu_monitor.mouse: PASS (172.21 s)
(13/15) type_specific.io-github-autotest-libvirt.libvirt_usb_hotplug_bench.stress.qemu_monitor.tablet: PASS (173.64 s)
(14/15) type_specific.io-github-autotest-libvirt.libvirt_usb_hotplug_bench.stress.qemu_monitor.disk: PASS (267.41 s)
(15/15) type_specific.io-github-autotest-libvirt.libvirt_usb_hotplug_bench.stress.attach_device.disk: PASS (391.05 s)
TOTAL TIME: 3771.78 s (01:02:51)
TESTS PASSED: 15
TESTS FAILED: 0
SUCCESS RATE: 100.00 %