staging: lustre: lnet: replace uninitialized_var

Checkpatch for some reason doesn't like the way
libcfs_str2net_internal. Lets just replace it with
nf being set to NULL instead

Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>