[smbfs.c]: Fix recently introduced memory leak

[Roland Illig]

Andrew V. Samoilov wrote:
> Hi Roland!
> 
> This patch should be applied some years ago, but I didn't abuse by huge patches...
> 

Hello Andrew,

I have applied a slight variant of your patch. Your patch didn't fix a 
memory leak (to my knowledge), but I discovered one while checking and 
applying your patch. But most of the patch has been committed.

Roland