eal: do not reset getopt lib

eal: do not reset getopt lib

Someone may need to call rte_eal_init() with a fake argc/argv array
in the middle of using getopt() to parse its own unrelated argc/argv
parameters. So getopt lib shouldn't be reset by rte_eal_init().

Now eal will always save optind, optarg and optopt (and optreset on
FreeBSD) at the beginning, initialize optind (and optreset on FreeBSD)
to 1 before calling getopt_long(), then restore all values after.

Suggested-by: Don Provan <dprovan@bivio.net>
Suggested-by: Bruce Richardson <bruce.richardson@intel.com>
Signed-off-by: Tiwei Bie <btw@mail.ustc.edu.cn>
Reviewed-by: Don Provan <dprovan@bivio.net>
Acked-by: Bruce Richardson <bruce.richardson@intel.com>
Acked-by: David Marchand <david.marchand@6wind.com>