Disallow DVD and Bluray ringbuffers for file transfers.

Following the changes to allow local paths for video playback, the
backend was trying to open a DVD or Bluray ringbuffer when asked for a
straight file transfer.

mythtv/programs/mythbackend/filetransfer.cpp

@@ -11,7 +11,7 @@
 FileTransfer::FileTransfer(QString &filename, MythSocket *remote,
                            bool usereadahead, int timeout_ms) :
     readthreadlive(true), readsLocked(false),
-    rbuffer(RingBuffer::Create(filename, false, usereadahead, timeout_ms)),
+    rbuffer(RingBuffer::Create(filename, false, usereadahead, timeout_ms, true)),
     sock(remote), ateof(false), lock(QMutex::NonRecursive),
     refLock(QMutex::NonRecursive), refCount(0), writemode(false)
 {