Patch from Mike Snitzer to fix return codes.

Patch from Mike Snitzer to fix return codes.

"I have a need to _really_ know if the interface was properly configured
via ifup so I made busybox's ifupdown pass the return codes through rather
than dropping them on the floor."

"All the functions in ifupdown.c return 1 on success and 0 on failure
(which happens to the opposite of standard practices but whatever).
So it is important for all these functions to not blindly return 1."

"The problem with blindly returning ret, even if it is != 1, is the
callers expect a 0 or 1 and accumulate the return codes.  So a function that
makes 3 calls to execute will have a value of 3 accumulated.  That value
of 1 (success) was almost always returned even if 1 of the commands in the
command sequence failed.  The attached patch fixes the lack of checking
to verify thar result == expected_reult."