Re #6371. Lower the logging level on connection.

In general, the calling factory class should be handling reporting
here. Specifically, I want to silently attempt a connection in the
background without the user seeing it.
Re #6371. Avoid trying to reload same file over and over.

I was having problems on the mac with this slot being invoked every
time the filename box lost focus, leading to getting stuck in a loop if
an invalid file had been loaded. For some reason I didn't see this on
RHEL6.
Re #6371. Probably a better clean-up order.
Merge branch 'feature/6371_step_scan_gui' into develop