Comment can't be added for Service Desk Customers via email due to lack of Add Comment permission by default

Steps to Reproduce

1. Create a user with valid email
2. Create a Service Desk with administrator
3. Go to the People tab and remove jira-users from the Service Desk Team
4. Login as the user(Service Desk Customer)
5. File a Service Desk request
6. When you receive the notification as the Service Desk Customer, reply directly to the notification with any comment

Expected Behaviour:

Mail handler should process that email and comment in that issue

Actual Behaviour:

Comment not added for the Service Desk customer

In Debug incoming log:

2014-04-25 23:28:03,542 DEBUG [testing] QuartzScheduler_Worker-0 ServiceRunner    mail capture S: +OK message follows
2014-04-25 23:28:03,715 DEBUG [testing] QuartzScheduler_Worker-0 ServiceRunner    mail capture User 'vicky' does not have permission to comment on an issue in project '10200'.
2014-04-25 23:28:03,717 DEBUG [testing] QuartzScheduler_Worker-0 ServiceRunner    mail capture Deleting Message: <CABuj-xkVgBSwF5PGN9L9VVBBwgnktmYEyMbiUgA_h9Nq9dMTMQ@mail.gmail.com>
2014-04-25 23:28:03,717 DEBUG [testing] QuartzScheduler_Worker-0 ServiceRunner    mail capture Closing folder
2014-04-25 23:28:03,741 DEBUG [testing] QuartzScheduler_Worker-0 ServiceRunner    mail capture Delivered-To: tecken90@gmail.com

Root Cause:

Default Service Desk permission didn't add Service Desk Customer to the Add Comment permission in the permission scheme.

Workaround:

Add Service Desk Customer into the Add Comment permission in the project's permission scheme