Duplicated keys on argdist per string

I was on an eBPF workshop by @goldshtn at SRECon Europe 2016 and ran into the following situation:

Running `argdist -z 4 -v -p $(pidof node) -C 'u:/usr/local/bin/node:http__server__request():char*:arg6'` to, hopefully, get a list of counts by path requested to the node.js server.

Doing the following test `for i in {1..10000}; do curl http://localhost:8080/hiiii; done` would cause the following output:

``` u:/usr/local/bin/node:http__server__request():char*:arg6
COUNT EVENT
196 arg6 = /hiiii
199 arg6 = /hiiii
[15:43:29]
u:/usr/local/bin/node:http__server__request():char*:arg6
COUNT EVENT
199 arg6 = /hiiii
224 arg6 = /hiiii
[15:43:30]
u:/usr/local/bin/node:http__server__request():char*:arg6
COUNT EVENT
199 arg6 = /hiiii
251 arg6 = /hiiii
[15:43:31]
u:/usr/local/bin/node:http__server__request():char*:arg6
COUNT EVENT
199 arg6 = /hiiii
251 arg6 = /hiiii
[15:43:32]
u:/usr/local/bin/node:http__server__request():char*:arg6
COUNT EVENT
199 arg6 = /hiiii
251 arg6 = /hiiii
[15:43:33]
u:/usr/local/bin/node:http__server__request():char*:arg6
COUNT EVENT
199 arg6 = /hiiii
251 arg6 = /hiiii
```

A bit more investigation with @goldshtn indicates that adding the flag `-z 4` fixes the problem.

I believe he mentioned that this could mean that there's some uninitialized data in the string used as the key.