Renames 'sign_out' method & removes its extra call
Renames 'sign_out' method & removes its extra call

* Renaming to 'sign_out_from_sipity' so its more specific and
easy to understand.
* Removing it from 'Browse ETD buttons' scenario because after clicking
'View Submitted ETDs' the browser is redirected to Curate, and these
specs need not cover curate functionility testing.

ndlib/QA_tests,ndlib/QA_tests,ndlib/QA_tests