Memory leaks in libc's nis_passwd() and nisgroup()

[pfg]

Summary

CID 1016715
CID 1016717

Resource leak (RESOURCE_LEAK)17. leaked_storage:
Variable result going out of scope leaks the storage it points to.

The code is somewhat tricky so it's not a good idea
free the variable before the return as we can cause
double free()s; instead free the memory just before
jumping to the label.

Test Plan

I don't generally use NIS, but that's the area that might most
likely be affected.

[pfg]

This comment was removed by pfg.

[delphij]

Looks reasonable to me.

[pfg]

Committed as rI279035.