save only global processes on global zone ps

Save only processes that are running in the global zone on Solaris.
Hopefully this can only happen if `res == NULL`, i.e. if `result == 0`.
Notice that the code can all be simplified to:
```
const void *pidp = (void *)(intptr_t) pid;
return pidp == SeqLookup(list, pidp, PidListCompare);
```