Fix formatting for documentation of nbd command line options.

Signed-off-by: Stefan Weil <weil@mail.berlios.de> 
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>



git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@5301 c046a42c-6fe2-441c-8c8c-71466251a162