Image upload validation requires restart after config change

• When setting max.file size to 6M, the default of 4M is used anyway
• Only using browsers without flash. Works correctly when flash is enabled
• Lowering the max.file.size does work (i.e. it limits the file size).

To reproduce:

• Set the property: max.file.size = 6M
  in: /hippo:configuration/hippo:frontend/cms/cms-services/imageValidationService
• Turn the flash plugin in your browser OFF
• Go to the images in CMS
• Upload an image between 4MB and 6MB (one is attached to the issue)
  Expected result: The image is uploaded
  Actual result: An error stating "Upload must be less than 4M"