recovery: Don't report unrecognized option in recovery_main.

recovery_main is only interested in a subset of options. Suppress the
warning for unrecognized options (which are likely intended for
recovery).

Fixes: 141239600
Test: On Pixel 3a, write `--security` flag into /misc and reboot
      recovery. Check that recovery_main no longer reports
      "unrecognized option" warning.
      # echo "recovery\n--security\n" | \
          dd of=/dev/block/by-name/misc conv=notrunc bs=1 seek=64
      # killall -9 recovery
      # cat /tmp/recovery.log
Test: Write `--show_text=foo` instead, and check that recovery reports
      "option `--show_text' doesn't allow an argument".
Change-Id: I1cb3a5ed6db91e41453b8aad00c8608f78ac1fa6