Allow certain error codes in test-dns.lua tests
Allow certain error codes in test-dns.lua tests

Matches the allowed errors in gnulib's test-getaddrinfo.c:
http://git.savannah.gnu.org/gitweb/?p=gnulib.git;a=blob;f=tests/test-getaddrinfo.c;hb=0b40814b815c65cf56f0938d27499d7962aac640#l90

luvit/luv,zhaozg/luv,luvit/luv,zhaozg/luv