CLEANUP: dns: Removing usless variable & assignation

In dns_send_query(), ret was set to 0 but always reassigned before the
usage so this initialisation was useless.

The send_error variable was created, assigned to 0 but never used. So
this variable is just useless by itself. Removing it.
diff --git a/src/dns.c b/src/dns.c
index 7f4c59a..c76637f 100644
--- a/src/dns.c
+++ b/src/dns.c
@@ -280,11 +280,10 @@
 {
 	struct dns_resolvers *resolvers;
 	struct dns_nameserver *nameserver;
-	int ret, send_error, bufsize, fd;
+	int ret, bufsize, fd;
 
 	resolvers = resolution->resolvers;
 
-	ret = send_error = 0;
 	bufsize = dns_build_query(resolution->query_id, resolution->query_type, resolution->hostname_dn,
 			resolution->hostname_dn_len, trash.str, trash.size);