[Reviewer: Andy] Make sas-client get a connection to SAS from the socket factory

This change makes sas-client use our new socket factory to get a connected socket in the right network namespace. I haven't made it a user exit - we are already not using the master branch and I don't think this is something we would ever contribute back to master, so it seemed easiest to just make new branch. 

Tested as follows (as part of a homestead build):

* Socket factory running: client successfully establishes a connection (checked with netstat)
* Socket factory not running: client periodically tries to get a connection. This fails gracefully.
* Socket factory running but SAS server name wrong (does not resolve): client periodically tries to get a connection. This fails gracefully. 
* Socket factory running but SAS server name wrong (server not listening on SAS port): client periodically tries to get a connection. This fails gracefully. 

Ditto, mutatis mutandi.