Description:
------------
Mysql error log is filled with this when using a persistent connection. 
2020-05-26T23:15:40.279047Z 281924791 [Note] Access denied for user 'root'@'10.0.0.2' (using password: NO)

The connection succeeds so I'm assuming internally there are multiple attempts to connect, one of which is without the pass. 
This error is logged in the mysql log not on the first connect, but on subsequent requests to a process with a persistent connection.  
Switching to non persistent connection ( removing the p: form host), connection also succeeds but no such error is logged.

Also reverting to php 7.1.33 with exactly the same configuration does not log the error when using persistent connection. (expected behaviour)

All test using production Server version: 5.7.28-31-log Percona Server


Test script:
---------------
<?php

$link = mysqli_connect("p:10.0.0.2", "root", "password");

if (!$link) {
    echo "Debugging errno: " . mysqli_connect_errno();
} else {
    echo "Success";
}
?>

Expected result:
----------------
No error log message in mysql.

Actual result:
--------------
2020-05-26T23:15:40.279047Z 281924791 [Note] Access denied for user 'root'@'10.0.0.2' (using password: NO)