tdeioslave/sftp: purge password in the destructor

This could be useful in case the destructor will be called before
openConnection()

Signed-off-by: Alexander Golubev <fatzer2@gmail.com>
(cherry picked from commit 21ce69f338)

tdeioslave/sftp/tdeio_sftp.cpp

@@ -788,6 +788,8 @@ sftpProtocol::~sftpProtocol() {
 
   /* cleanup and shut down cryto stuff */
   ssh_finalize();
+
+  purgeString(mPassword);
 }
 
 void sftpProtocol::setHost(const TQString& h, int port, const TQString& user, const TQString& pass) {