libutil: fix memory leak in login_cap

[khng]

Summary

cgetstr() allocates memory to the string and sends it back to
the caller. Caller of cgetstr() is supposed to free that memory.

Sponsored by: Hewlett Packard Enterprise
MFC after: 3 days

[des]

Your use of “Obtained from” is incorrect, unless “Hewlett Packard Enterprise” is the name of a piece of open-source software I've never heard of that has a copy of our libutil and already had this patch. You probably want to use “Sponsored by” instead.

[khng]

In D54526#1246414, @des wrote:

Your use of “Obtained from” is incorrect, unless “Hewlett Packard Enterprise” is the name of a piece of open-source software I've never heard of that has a copy of our libutil and already had this patch. You probably want to use “Sponsored by” instead.

I just changed it to "Sponsored by:".

[des]

lib/libutil/login_cap.c

490

I refer you to login_cap(3):

Note that with all functions in this group, you should not call free(3)
on any pointers returned.  Memory allocated during retrieval or
processing of capability tags is automatically reused by subsequent calls
to functions in this group, or deallocated on calling login_close().