Bug 21500: Remove warnings in rotating collections

Bug 21500: Remove warnings in rotating collections

To test:
- Go to Tools > Rotating collections
=> FAIL: Some warinings on the logs
- Apply this patch
- Reload page
=> SUCCESS: No warinings
- Sign off :-D

Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
(cherry picked from commit 40803d30359f347417999429b612fcece9fc96f9)
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>