MDEV-37893 - main.public_privileges fails sporadically

Test output was affected by incompletely closed preceding connections.

Make test agnostic to concurrent connections by querying
information_schema.processlist only for connections that it uses.

Author: svoj

mysql-test/main/public_privileges.result

@@ -84,7 +84,7 @@ create database testdb;
 use testdb;
 create procedure p1 () select 1;
 connect  testuser,localhost,testuser,,;
-select user,db from information_schema.processlist where user='root';
+select user,db from information_schema.processlist where id=$default_id;
 user	db
 call testdb.p1();
 ERROR 42000: execute command denied to user 'testuser'@'%' for routine 'testdb.p1'
@@ -93,7 +93,7 @@ GRANT PROCESS ON *.* to PUBLIC;
 GRANT EXECUTE ON testdb.* to PUBLIC;
 disconnect testuser;
 connect  testuser,localhost,testuser,,;
-select user,db from information_schema.processlist where user='root';
+select user,db from information_schema.processlist where id=$default_id;
 user	db
 root	testdb
 call testdb.p1();
@@ -104,7 +104,7 @@ disconnect testuser;
 # check that the privileges are correctly read by acl_load
 flush privileges;
 connect  testuser,localhost,testuser,,;
-select user,db from information_schema.processlist where user='root';
+select user,db from information_schema.processlist where id=$default_id;
 user	db
 root	testdb
 call testdb.p1();

mysql-test/main/public_privileges.test

@@ -78,10 +78,11 @@ create user testuser;
 create database testdb;
 use testdb;
 create procedure p1 () select 1;
+let $default_id= `select connection_id()`;
 
 connect (testuser,localhost,testuser,,);
 
-select user,db from information_schema.processlist where user='root';
+evalp select user,db from information_schema.processlist where id=$default_id;
 --error ER_PROCACCESS_DENIED_ERROR
 call testdb.p1();
 
@@ -94,7 +95,7 @@ GRANT EXECUTE ON testdb.* to PUBLIC;
 disconnect testuser;
 connect (testuser,localhost,testuser,,);
 
-select user,db from information_schema.processlist where user='root';
+evalp select user,db from information_schema.processlist where id=$default_id;
 call testdb.p1();
 
 connection default;
@@ -105,7 +106,7 @@ flush privileges;
 
 connect (testuser,localhost,testuser,,);
 
-select user,db from information_schema.processlist where user='root';
+evalp select user,db from information_schema.processlist where id=$default_id;
 call testdb.p1();
 
 connection default;