Don't forget to flush XLOG_PARAMETER_CHANGE record.

Backpatch to 9.0 where XLOG_PARAMETER_CHANGE record was instroduced.

src/backend/access/transam/xlog.c

@@ -8446,6 +8446,7 @@ XLogReportParameters(void)
 		{
 			XLogRecData rdata;
 			xl_parameter_change xlrec;
+			XLogRecPtr	recptr;
 
 			xlrec.MaxConnections = MaxConnections;
 			xlrec.max_prepared_xacts = max_prepared_xacts;
@@ -8457,7 +8458,8 @@ XLogReportParameters(void)
 			rdata.len = sizeof(xlrec);
 			rdata.next = NULL;
 
-			XLogInsert(RM_XLOG_ID, XLOG_PARAMETER_CHANGE, &rdata);
+			recptr = XLogInsert(RM_XLOG_ID, XLOG_PARAMETER_CHANGE, &rdata);
+			XLogFlush(recptr);
 		}
 
 		ControlFile->MaxConnections = MaxConnections;