Merge pull request #587 from zhouqt/usb

qemu: Filter some usb test cases for RHEL guests/host

qemu/tests/cfg/usb.cfg

@@ -20,6 +20,9 @@
             usb_max_port_usbtest = 6
             drive_format_stg = "usb2"
         - xhci:
+            no RHEL.3
+            no RHEL.4
+            no RHEL.5
             usb_type_usbtest = nec-usb-xhci
             usb_controller = xhci
             usb_max_port_usbtest = 4
@@ -87,6 +90,7 @@
             product = "QEMU USB CCID"
         - usb_audio:
             no Host_RHEL.6
+            no Host_RHEL.7
             only usb_boot, usb_reboot, usb_hotplug
             usb_type = usb-audio
             info_usb_name = "QEMU USB Audio"