x86-run: correct a typo 'qemsystem' -> 'qemusystem'

Before this fix, you should always get error info as below when running 'x86-run' script.
"QEMU binary has no support for test device. Exiting."

Signed-off-by: Yongjie Ren <yongjie.ren@intel.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>