Ensure HTTP transport does not try to use "persistence" (check if still an issue)

[alanseiden]

Check on this to see if still relevant:

Remove need for $conn->setIsPersistent(true), because there is no sense of “persistence” when HTTP transport used, so errors occur if a close/disconnect can be sent. Same issue may occur with PECL transport because there's no true “connection.”

[alanseiden]

Notes:

• The purpose of passing a persistence flag into the constructor: To let the toolkit create its own database transport connection and make it a persistent connection.
• The persistence flag does not serve any purpose other than telling database connection code whether to make the connection persistent.
• We do refer to the value of the persistence flag for logging, but its value could be looked up by getting the resource type or PDO persistence attribute.
• I suggest we create a new issue that seeks to look up the persistence value when necessary (see previous bullet point), but no longer passes it around or needing a getter or setter.