If-None-Match logic for CTweb
If-None-Match logic for CTweb

Don’t send duplicates if-none-match in header.  (Preceding commit had
most of the actual changes).

cycronix/cloudturbine,jpw-erigo/cloudturbine,cycronix/cloudturbine,jpw-erigo/cloudturbine,jpw-erigo/cloudturbine,cycronix/cloudturbine,cycronix/cloudturbine,jpw-erigo/cloudturbine