spice usb storage insertion tests

[lkocman]

This issue needs to be split. Can I have master issues? (or dependencies anyway). I just said "usb storage" to make this a little more specific, but we should support other common usage devices as well. anything that is easy to automate, so anything that we can emulate.

A test would have to:
launch the client vm that would provide the device to be remoted. Have it include a usb storage device.
launch the target vm that would include the usbredir device.
launch a spice client inside a vm.
check that the target can access the device on the client (create a file in client, read it in target, write to it in target, read in client).

Upstream: autotest#160

[lkocman]

alon: you won't be creating virtual devices in linux, but with qemu:
qemu-client:
dd if=/dev/zero of=/tmp/disk.raw
create partition table, file system, put some dummy files to find later.
qemu -usbdevice disk:/tmp/disk.raw
inside vm:
remote-viewer
qemu-guest: launch with -usbredir

[lkocman]

depends on Issue #2