MH-9387 -- made sure that the move operation succeeds by removing first whatever is at the destination

git-svn-id: https://opencast.jira.com/svn/MH/trunk@13837 e6edf6fb-f266-4316-afb4-e53d95876a76
MH-9443 -- fixed broken test

git-svn-id: https://opencast.jira.com/svn/MH/trunk@13839 e6edf6fb-f266-4316-afb4-e53d95876a76