Prevent PHPMailer from testing if TLS is available when smtp_options["secure"] TLS is set to False

Even when smtp_options["secure"] is set to false, PHPMailer is testing if the smtp server supports TLS and force it in that case.

• The configuration set by the user can be bypassed by this 3rdparty lib
• This test generates false positives => this is how we detected it

We use this PHPMailer public attribute to bypass this messy test.