Utility user was visible in performance_schema.threads.

While testing PS-5216, following observation is noticed. Details are furnished below:
 
1. I have 2 connected client sessions. Both are regular users. To verify:
mysql> select thread_id,PROCESSLIST_USER,instrumented,history from performance_schema.threads where type='FOREGROUND' and connection_type='Socket';
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2 rows in set (0.00 sec)
 
2. Now, I connect a client session from a utility user. To verify:
mysql> select thread_id,PROCESSLIST_USER,instrumented,history from performance_schema.threads where type='FOREGROUND' and connection_type='Socket';
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3 rows in set (0.00 sec)
 
3. Enabling the instrumentation for utility user session so that we can record the session activity:
mysql> update performance_schema.threads set instrumented='YES' where thread_id=54;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0
 
mysql> select thread_id,PROCESSLIST_USER,instrumented,history from performance_schema.threads where type='FOREGROUND' and connection_type='Socket';
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3 rows in set (0.00 sec)
 
4. Now I do an insert from utility user session:
mysql> insert into t2 values (1,'Mohit');
Query OK, 1 row affected (0.08 sec)
 
5.
mysql> select thread_id, sql_text from performance_schema.events_statements_current where thread_id=54;
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1 row in set (0.00 sec)
 
 
The expected behaviour should be that there should not be a thread for the utility user client session