Refactored connection managment once again. It should be much cleaner now.  More in details.

* Moved sftp_session and sftp_handle to private section of file sending function.
* Set session timeout to 30 seconds.
* Improved new files detection for high network load cases.
* Strongly improved stability of SFTP trasfers when running Synshot on machine with high network load.
* More useful info about what's going on.

Signed-off-by: Daniel (dmilith) Dettlaff <dmilith@verknowsys.com>