MDEV-23752 SHOW EXPLAIN FOR thd waits for sleep

fix main.processlist_notembedded test

* before EXPLAINing `select sleep` wait for select to start
  (fixes "Target is not running an EXPLAINable command")
* after killing sleep, wait for it to die
  (fixes test failures on --repeat when old sleep shows on a test rerun)

* unify with 10.3, copy minor changes from there
  (`--echo End of 5.5` vs `--echo # End of 5.5`, etc)

mysql-test/r/processlist_notembedded.result

 #
 # MDEV-20466: SHOW PROCESSLIST truncates query text on \0 bytes
 #
-connect  con1,localhost,root,,;
+connect con1,localhost,root;
 connection con1;
 SET DEBUG_SYNC= 'before_join_optimize SIGNAL in_sync WAIT_FOR go';
 connection default;
@@ -13,17 +13,22 @@ user
 disconnect con1;
 connection default;
 SET DEBUG_SYNC = 'RESET';
-End of 5.5 tests
+#
+# End of 5.5 tests
+#
 #
 # MDEV-23752: SHOW EXPLAIN FOR thd waits for sleep
 #
-connect  con1,localhost,root,,;
-select sleep(100000);;
+connect con1,localhost,root;
+select sleep(100000);
 connection default;
-SHOW EXPLAIN FOR con_id;
+SHOW EXPLAIN FOR $con_id;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
 Warnings:
 Note	1003	select sleep(100000)
-KILL QUERY con_id;
+KILL QUERY $con_id;
+disconnect con1;
+#
 # End of 10.2 tests
+#

mysql-test/t/processlist_notembedded.test

-source include/have_debug.inc;
 source include/have_debug_sync.inc;
 source include/not_embedded.inc;
 source include/count_sessions.inc;
@@ -7,7 +6,7 @@ source include/count_sessions.inc;
 --echo # MDEV-20466: SHOW PROCESSLIST truncates query text on \0 bytes
 --echo #
 
-connect (con1,localhost,root,,);
+connect con1,localhost,root;
 
 connection con1;
 
@@ -37,24 +36,26 @@ connection default;
 
 SET DEBUG_SYNC = 'RESET';
 
-source include/wait_until_count_sessions.inc;
-
---echo End of 5.5 tests
+--echo #
+--echo # End of 5.5 tests
+--echo #
 
 --echo #
 --echo # MDEV-23752: SHOW EXPLAIN FOR thd waits for sleep
 --echo #
 
---connect (con1,localhost,root,,)
+--connect con1,localhost,root
 --let $con_id = `SELECT CONNECTION_ID()`
---send select sleep(100000);
+--send select sleep(100000)
 
 --connection default
+let $wait_condition= SELECT COUNT(*)=1 FROM information_schema.processlist where state='User sleep';
+source include/wait_condition.inc;
+evalp SHOW EXPLAIN FOR $con_id;
+evalp KILL QUERY $con_id;
+disconnect con1;
+source include/wait_until_count_sessions.inc;
 
---replace_result $con_id con_id
-eval SHOW EXPLAIN FOR $con_id;
-
---replace_result $con_id con_id
-eval KILL QUERY $con_id;
-
+--echo #
 --echo # End of 10.2 tests
+--echo #