Implement P9_TWSTAT support.
This gets file and directory creation to work.

[jvrao@linux.vnet.ibm.com: strdup to qemu_strdup conversion]
[aneesh.kumar@linux.vnet.ibm.com: v9fs_fix_path]
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>
Signed-off-by: NAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>