[FIX] tikimail: Remove previous Content-type header (if there was one) before adding a new one - repeated use of the same instance added a new one each time the mail body was set
[FIX] tikimail: Remove previous Content-type header (if there was one) before adding a new one - repeated use of the same instance added a new one each time the mail body was set

git-svn-id: a7fabbc6a7c54ea5c67cbd16bd322330fd10cc35@60083 b456876b-0849-0410-b77d-98878d47e9d5

oregional/tiki,oregional/tiki,oregional/tiki,tikiorg/tiki,oregional/tiki,tikiorg/tiki,tikiorg/tiki,tikiorg/tiki