rpc: Bump maximum message size to 32M

While most of the APIs are okay with 16M messages, the bulk stats API
can run into the limit in big configurations. Before we devise a new
plan for this, bump this limit slightly to accomodate some more configs.

src/rpc/virnetprotocol.x

@@ -40,13 +40,13 @@ const VIR_NET_MESSAGE_INITIAL = 65536;
 const VIR_NET_MESSAGE_LEGACY_PAYLOAD_MAX = 262120;
 
 /* Maximum total message size (serialised). */
-const VIR_NET_MESSAGE_MAX = 16777216;
+const VIR_NET_MESSAGE_MAX = 33554432;
 
 /* Size of struct virNetMessageHeader (serialised)*/
 const VIR_NET_MESSAGE_HEADER_MAX = 24;
 
 /* Size of message payload */
-const VIR_NET_MESSAGE_PAYLOAD_MAX = 16777192;
+const VIR_NET_MESSAGE_PAYLOAD_MAX = 33554408;
 
 /* Size of message length field. Not counted in VIR_NET_MESSAGE_MAX
  * and VIR_NET_MESSAGE_INITIAL.