Add additional logging for importing course from git

(cherry picked from commit 7d861245864aa13d0feedbd18086a9f054428a96)

Conflicts:
	lms/djangoapps/dashboard/management/commands/tests/test_git_add_course.py
Correct exception raising bug for non global staff accessing missing course git logs

(cherry picked from commit 3aecac7adb9fb161402b7b57feec5a7f40e1f07a)