[Patch] Don't say receipt was sent when receipt was not asked to be sent

> When editing a membership status, even if you don't check the "send receipt" box, the popup confirmation message after saving says "A confirmation and receipt has been sent to $address". I checked in the mailserver logs and nothing seems to have been sent.

Please see the attached patch.

This patch has been tested on an otherwise modified version of CiviCRM 4.6.24. The patch was initially developed by someone else for a version older than the version we are currently using. We hope that you find this contribution useful.

Thank you.