qemu.tests.cfg: Update usb_reply_msg for RHEL6 host in usb

Now no output from monitor for negative test on RHEL.6 host,
so update usb_reply_msg config.

Signed-off-by: Shuping Cui <scui@redhat.com>
qemu.tests: Small bugs fix in format_disk

Sometimes the output include some specific control character, like: ^H,
so update check content method.

Signed-off-by: Shuping Cui <scui@redhat.com>
qemu.tests.cfg: Update usb_sleep_time config for usb.cfg

usb device verify need some time to let the guest os
to init the device after hotpluging.

Signed-off-by: Shuping Cui <scui@redhat.com>
Merge pull request #113 from spcui/usb_fix

usb small bugs fix