[Toybox] ifconfig: simplify exit with help

[Rob Landley]

On 04/14/2013 01:03:51 AM, Isaac Dunham wrote:
> This patch simplifies exiting with help in ifconfig.
> Has no change on binary size, but loses 37 lines.
> 
> Also means that ifconfig --help exits cleanly with help disabled.

I screwed this up on my first attempt at applying it, but fixed it up  
in a later commit. (It conflicted with me splitting help infrastructure  
out from the help command, which upon further consideration was a good  
suggestion.)

Rob