libhandle: Guard against string overflow in path_to_fspath()

libhandle: Guard against string overflow in path_to_fspath()

path_to_fspath does a blind strcpy into an array of
MAXPATHLEN; we should be sure to limit this so that it
does not go over the size of the array.

I don't think I see a way to get here today with a too-long
path, but I don't think it'll hurt to be defensive.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Mark Tinguely <tinguely@sgi.com>
Signed-off-by: Mark Tinguely <tinguely@sgi.com>