MDEV-31609 mtr: only print session tracking from the last statement

We do this by checking server status. By doing this we avoid printing
session tracking info from previous (but not the last) statement.

The change is from Sergei Golubchik

client/mysqltest.cc

@@ -7948,6 +7948,8 @@ static const char *trking_info_desc[SESSION_TRACK_END + 1]=
 
 static void append_session_track_info(DYNAMIC_STRING *ds, MYSQL *mysql)
 {
+ if (!(mysql->server_status & SERVER_SESSION_STATE_CHANGED))
+ return;
 #ifndef EMBEDDED_LIBRARY
  for (unsigned int type= SESSION_TRACK_BEGIN; type <= SESSION_TRACK_END; type++)
  {

mysql-test/main/session_tracker_last_gtid.result

@@ -11,10 +11,6 @@ create table t1 (a int) engine=innodb;
 select @@last_gtid;
 @@last_gtid
 0-1-1000
--- Tracker : SESSION_TRACK_SYSTEM_VARIABLES
--- last_gtid
--- 0-1-1000
-
 insert into t1 values (1);
 -- Tracker : SESSION_TRACK_SYSTEM_VARIABLES
 -- last_gtid
@@ -23,10 +19,6 @@ insert into t1 values (1);
 select @@last_gtid;
 @@last_gtid
 0-1-1001
--- Tracker : SESSION_TRACK_SYSTEM_VARIABLES
--- last_gtid
--- 0-1-1001
-
 drop table t1;
 -- Tracker : SESSION_TRACK_SYSTEM_VARIABLES
 -- last_gtid