Fixed consistency of wrongly using java.io.FileNotFoundException instead of preferred org.apache.commons.vfs2.FileNotFoundException (#638)

Author: mareksunda

commons-vfs2/src/main/java/org/apache/commons/vfs2/provider/ftp/FtpFileObject.java

@@ -16,7 +16,6 @@
  */
 package org.apache.commons.vfs2.provider.ftp;
 
-import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
@@ -37,6 +36,7 @@
 import org.apache.commons.net.ftp.FTPFile;
 import org.apache.commons.vfs2.FileName;
 import org.apache.commons.vfs2.FileNotFolderException;
+import org.apache.commons.vfs2.FileNotFoundException;
 import org.apache.commons.vfs2.FileObject;
 import org.apache.commons.vfs2.FileSystemException;
 import org.apache.commons.vfs2.FileType;