post sample rate changes directly on DSP input message queue. Removed sample source output queue entirely as it was not reliable under stress

plugins/samplesource/filesource/filesourceinput.cpp

@@ -20,6 +20,7 @@
 
 #include "util/simpleserializer.h"
 #include "dsp/dspcommands.h"
+#include "dsp/dspengine.h"
 #include "dsp/filesink.h"
 
 #include "filesourcegui.h"
@@ -276,7 +277,7 @@ bool FileSourceInput::applySettings(const Settings& settings, bool force)
 		}
         
 		DSPSignalNotification *notif = new DSPSignalNotification(m_sampleRate, m_centerFrequency);
-		getOutputMessageQueue()->push(notif);                
+		DSPEngine::instance()->getInputMessageQueue()->push(notif);
 
 		qDebug() << "FileSourceInput::applySettings:"
 				<< " file name: " << settings.m_fileName.toStdString().c_str()