DNS: Fixes for the DNS query module

Fixes for the DNS query module, including:

 (1) Use 'negative' instead of '-ve' in the documentation.

 (2) Mark the kdoc comment with '/**' on dns_query().

Reported-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>