nscd: Drop local address tuple variable [BZ #29607]

When a request needs to be resent (e.g. due to insufficient buffer
space), the references to subsequent tuples in the local variable are
stale and should not be used.  This used to work by accident before, but
since 1d495912 it no longer does.  Instead of trying to reset it, just
let gethostbyname4_r write into TUMPBUF6 for us, thus maintaining a
consistent state at all times.  This is now consistent with what is done
in gaih_inet for getaddrinfo.

Resolves: BZ #29607
Reported-by: Holger Hoffstätte <holger@applied-asynchrony.com>
Tested-by: Holger Hoffstätte <holger@applied-asynchrony.com>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
(cherry picked from commit 6e33e5c4)