Enrol methods and enrolments not being restored anymore

This required own testing + repeat the testing performed @ MDL-26841 (because of being a regression). A) Own testing: Create one course, enable manual enrolments and enrol 1 teacher and 2 students. As admin (that have perms to backup users and enrolments) perform one course backup. As admin, restore that backup file into new course. TEST: The manual enrolment method is enabled in the restored course and the 1 teacher and 2 students are enrolled as they where in the source course. B) Original testing: Create 2 courses: "source" and "target" In "source" add various enrolment plugins (manual, guest, self...) and add 1-2 manual enrolments (students). Add also 1 forum and ignite some discussions with those students. In "target" add manual enrolment only with 1 student (different student from the ones in point 2). Logged as admin, perform one import in "target", picking "source" as origin. Select the forum activity and import. TEST: The operations ends without error. TEST: The forum activity has been imported but without any discussion. TEST: Look at "target" enrolment methods. Only the original "manual" is there and none of the enrolment methods in "source" have been imported.