rpc: Allow up to 256K records to be returned per domain from virConnectGetAllDomainStats.

The number of records that virConnectGetAllDomainStats can return per
domain is currently limited to 4096.  This is quite low -- for
example, a single guest with ~320 disks will hit this limit.  This
increases the limit to make it much larger.  Note that
VIR_NET_MESSAGE_MAX still protects the total message size in the case
where there are many domains and many disks per domain.

I tested this using a guest with 500 disks with no issues.
Signed-off-by: NRichard W.M. Jones <rjones@redhat.com>
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1440683

src/remote/remote_protocol.x

@@ -233,7 +233,7 @@ const REMOTE_DOMAIN_FSFREEZE_MOUNTPOINTS_MAX = 256;
 const REMOTE_NETWORK_DHCP_LEASES_MAX = 65536;
 
 /* Upper limit on count of parameters returned via bulk stats API */
-const REMOTE_CONNECT_GET_ALL_DOMAIN_STATS_MAX = 4096;
+const REMOTE_CONNECT_GET_ALL_DOMAIN_STATS_MAX = 262144;
 
 /* Upper limit of message size for tunable event. */
 const REMOTE_DOMAIN_EVENT_TUNABLE_MAX = 2048;