Revert "HACK: Skip provisioning every time mailbox is opened"

This reverts commit c61f63c5c40fa3e964b281c1ad66635b92b8802f.
mapistore/oxio: Handle return values from Indxing.uri_for_fmid gfacefully
mapistore/oxio: move logger initialization in separate function

It is still a global logger - not very nice but will do the job
mapistore/python: Print out the error on Folder.open_message() failure
mapistore/oxio: Listing and open messages implementation