-retry option is wrong

[nil0x42]

After some testing, i noticed that -retry actually behaves like a -num-tries option.

Indeed, running dnsx with -retry 0, we should exepct it to try once, then dont REtry at all. If the int defines the total number of tries, it should then be renamed into -tries or -num-tries to avoid confusion. Otherwise the helper should be a bit more specific.