- remove useless variable "status" from init_main.

- remove useless variable "status" from init_main.
http://www.opengroup.org/onlinepubs/009695399/functions/waitpid.html suggests
that we need not specify a status if we don't want, and we don't.
"If wait() or waitpid() return because the status of a child process is available, these functions shall return a value equal to the process ID of the child process. In this case, if the value of the argument stat_loc is not a null pointer, information shall be stored in the location pointed to by stat_loc.  "
   text    data     bss     dec     hex filename
   5391      32       8    5431    1537 init/init.o.06
   5379      32       8    5419    152b init/init.o