app_voicemail: when forwarding a message, play vm-msgforwarded instead of vm-msgsaved

In the last release of sounds, 1.4.25 we added a vm-msgforwarded prompt for various core languages. Now we use that prompt.

(issue ASTERISK-21413)
(closes issue ASTERISK-21413)
Reported by: netwrkr
Tested by: newtonr


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@403106 65c4cc65-6c06-0410-ace0-fbb531ad65f3