resolv: Unify sockaddr union

Merge the following unions into a single union.
sockaddr_union
_sockaddr_union
res_sockaddr_union

Test: netd_{unit,integration}_test pass
Change-Id: I46685e7380dd25070ccd9eaf5387efde91cded8a
diff --git a/resolv/res_state_ext.h b/resolv/res_state_ext.h
index cf906f0..6ed3398 100644
--- a/resolv/res_state_ext.h
+++ b/resolv/res_state_ext.h
@@ -7,7 +7,7 @@
 
 // TODO: consider inlining into res_state
 struct res_state_ext {
-    union res_sockaddr_union nsaddrs[MAXNS];
+    sockaddr_union nsaddrs[MAXNS];
     struct sort_list {
         int af;
         union {