make plugins.processlist more robust

mysql-test/suite/plugins/r/processlist.result

 create table t1 (a int) engine=innodb;
 start transaction;
 insert t1 values (1);
-state from show engine innodb status
- 
-state from show processlist
+state from show engine innodb status, must be empty
  
 drop table t1;

mysql-test/suite/plugins/t/processlist.test

@@ -8,11 +8,12 @@ start transaction;
 insert t1 values (1);
 let id=`select connection_id()`;
 connect con2,localhost,root;
+let $wait_condition=select state='' from information_schema.processlist where id = $id;
+--source include/wait_condition.inc
 replace_regex /\"/-/; #"
 let s=`show engine innodb status`;
 disable_query_log;
-eval select regexp_replace("$s", '(?s)^.*MySQL thread id $id,.*root([^\n]*)\n.*', '\\\\1') as `state from show engine innodb status`;
-eval select state as `state from show processlist` from information_schema.processlist where id = $id;
+eval select regexp_replace("$s", '(?s)^.*MySQL thread id $id,.*root([^\n]*)\n.*', '\\\\1') as `state from show engine innodb status, must be empty`;
 enable_query_log;
 disconnect con2;
 connection default;