qemu.tests: Update some config for negative test

Update some negative config in different version of qemu.

Signed-off-by: Shuping Cui <scui@redhat.com>
qemu.tests: Improve check removable option

In different version of qemu, the output of removable
in qtree are not same, so update check method to
make a transfer for on/off, yes/no, true/false.

Signed-off-by: Shuping Cui <scui@redhat.com>
Merge pull request #205 from spcui/usb_fix

qemu.tests: Update some config for usb test