cleanup: save 60 lines/100 bytes by combining two mostly duplicate functions.

Eliminate two mostly duplicate functions (nfs_parse_simple_hostname()
and nfs_parse_protected_hostname()) and instead just make the calling
function (nfs_parse_devname()) do everything.

Signed-off-by: Rob Landley <rlandley@parallels.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>