Fixes in maintainer

[KirilKabakchiev]

• fix logging and missing correlation ids when maintainer schedules an operation
• fix namings of maintainer functors
• fix maintainer setting deletion scheduled on stuck updates
• fix maintainer trying to do orphan mitigation after a stuck update operation has been marked as failed
• fix scheduler trying to create a new operation when invoked by maintainer even though one already exists (when maintainer reschedules an operation which is not the last operation for this resource because several hours have passed and newer operations have appeared after the one that is being rescheduled)

[coveralls]

Coverage decreased (-0.04%) to 86.819% when pulling b131a7ed79ac79f199f1b903494db4257095b0d8 on fix-maintainer into c683e1cb21d4ded9d07be28038d49b92d6094a12 on master.