InstructorFeedbackEditPageUiTest fails in masquerade mode #2417

Fixes #2417
Fixes #2428 (typo in error message)

One test still fails, instructorFeedbackResultsPageUiTest, related to profile picture, which already is failing in master. (org.openqa.selenium.NoSuchElementException: Unable to locate element: {"method":"css selector","selector":".popover-content > img"}
)