Change the handling behavior of emails containing 4 byte characters to avoid random increments of issue numbers

Summary

Due to JIRA not being able to handle 4 byte characters when using MySQL (JRA-36135), emails which contains 4 byte characters will fail to be created. However JIRA keeps on trying to process the email and each time it does, issuenum will increase by 1 although a ticket is never really created

Suggestion

Avoid this from happening. Some suggestions are

1. Either stop processing kind of mail the moment it fails once to avoid issue number from increasing OR
2. Change the process such that it will only increment issuenum when an issue is successfully created

Temporary Workaround

Remove the email containing the 4 byte character by either moving it to another folder or deleting it.

Permanent Workaround

See JRA-36135 - upgrade to Jira 8 or modify the database