After recording only silence for a voicemail prepending, restore backup files.

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.4@298683 65c4cc65-6c06-0410-ace0-fbb531ad65f3

apps/app_voicemail.c

@@ -5217,6 +5217,10 @@ static int vm_forwardoptions(struct ast_channel *chan, struct ast_vm_user *vmu,
 				ast_channel_setoption(chan, AST_OPTION_RXGAIN, &record_gain, sizeof(record_gain), 0);
 
 			cmd = ast_play_and_prepend(chan, NULL, msgfile, 0, vmfmts, &prepend_duration, 1, silencethreshold, maxsilence);
+			if (cmd == 'S') {
+				ast_filerename(backup, msgfile, NULL);
+			}
+
 			if (record_gain)
 				ast_channel_setoption(chan, AST_OPTION_RXGAIN, &zero_gain, sizeof(zero_gain), 0);