Remove directory contents if it exists

src/freedombone-app-matrix

     if [ ! -d $INSTALL_DIR/sydent ]; then
         mkdir -p $INSTALL_DIR/sydent
     fi
+    if [ -d $INSTALL_DIR/sydent ]; then
+        rm -rf $INSTALL_DIR/sydent/*
+    fi
     pip install --upgrade --process-dependency-links . -b $INSTALL_DIR/sydent
     if [ ! "$?" = "0" ]; then
         echo $'Failed to install matrix identity server'