Fix use of half-initialized result in getaddrinfo when using nscd (bug 16743)

This fixes a bug in the way the results from __nscd_getai are collected:
for every returned result a new entry is first added to the
gaih_addrtuple list, but if that result doesn't match the request this
entry remains uninitialized.  So for this non-matching result an extra
result with uninitialized content is returned.

To reproduce (with nscd running):

	$ getent ahostsv4 localhost
	127.0.0.1       STREAM localhost
	127.0.0.1       DGRAM
	127.0.0.1       RAW
	(null)          STREAM
	(null)          DGRAM
	(null)          RAW