This reverts commit f97f0525, reversing
changes made to 800bcd8e.

The new masquerading code introduced in PR #8775 adds a new attribute to
CourseMasquerade objects stored in the user's session.  When users who have
active masquerading configuration access instances with the new code, and
AttributeError occurs when trying to access the attribute user_name.

This fix ensures that CourseMasquerade objects receive all required attributes
when they are unpickled from the session.

TNL-651

Conflicts:
	lms/djangoapps/courseware/views.py
	lms/templates/courseware/course_navigation.html