The commonplace employer practice of asking employees to refrain from discussing internal investigations with co-workers has come under attack from the National Labor Relations Board.  In Banner Health Sys. d/b/a Banner Estrella Med., Ctr., 358 N.L.R.B. No. 93, 7/30/12, the National Labor Relations Board (“NLRB”) held in a 2 to 1 decision that employees&rsquo…