Get the current file from the editor, not the filemanager. The later
does not get updated for temporary files like those created by git
blame, leaving the file-based actions in the VCSes enabled when viewing
those temporary files, triggering actions on the last real file that
was visible.

Task-number: QTCREATORBUG-6250
Change-Id: I5c2d3c62805f69bc8e103f0776cd6796332f606c
Reviewed-on: http://codereview.qt-project.org/6175


Sanity-Review: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Daniel Teske <daniel.teske@nokia.com>