Guard Process.kill pid 1 spec in case user owns it

In some environments, the user running the spec might own pid `1` (even without being root).  It's also possible this spec could be run from _as_ pid `1`.  This is the case with Docker, in which the command you pass to `docker run` is run as pid 1.

```
jemc@localhost~/1/docker> sudo docker run -t -i rubinius ps
  PID TTY          TIME CMD
    1 ?        00:00:00 ps
```

In this situation, MRI will allow killing of pid 1 without exception (and so will `kill -9 1`).

The spec needs to guard this test and skip it when the current user owns pid 1.
I don't know a way to set up a process you don't have permission to kill, so we're left with something like killing id 1.

We should be able to use Process methods to check, shouldn't we?

It may seem like overkill (no pun intended) in this case to make a specific guard for this, but one of the things I try to avoid is arbitrary conditionals in the specs.