qemu.test.format_disk: Add more steps in this test

This test script just leaves the disk(s) in mounted
status after read operation, this patch adds 2 more
steps after read: umount the disk and check dmesg
output.

CC: Xu Tian <xutian@redhat.com>
Signed-off-by: Qingtang Zhou <qzhou@redhat.com>
qemu.tests.cfg: Add umount_cmd config for format_disk test

And add quote mark for config parameters.

Signed-off-by: Qingtang Zhou <qzhou@redhat.com>
qemu.tests.format_disk: Update the cmd of read/write data

This patch makes the read/write cmd fully configurable.

Signed-off-by: Qingtang Zhou <qzhou@redhat.com>
qemu.tests.usb_storage: Do io test with format_disk script

Signed-off-by: Qingtang Zhou <qzhou@redhat.com>
qemu.tests.usb_storage: Add a helper function to get usb disk

Signed-off-by: Qingtang Zhou <qzhou@redhat.com>
qemu.tests.usb_storage: make this script work for win guest

Signed-off-by: Qingtang Zhou <qzhou@redhat.com>
qemu: systemtap_tracing - Change a variant name to avoid conflicts

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>