Remove dns_badcache usage in the resolver (lame-ttl)

Remove dns_badcache usage in the resolver (lame-ttl)

The lame-ttl processing was overriden to be disabled in the config,
but the code related to the lame-ttl was still kept in the resolver
code.  More importantly, the DNS_RESOLVER_BADCACHETTL() macro would
cause the entries in the resolver badcache to be always cached for at
least 30 seconds even if the lame-ttl would be set to 0.

Remove the dns_badcache code from the dns_resolver unit, so we save some
processing time and memory in the resolver code.