Fix permissions when copying from ObjectStorage

Make sure that when a user copy a file from a directory they don't have
all permissions to a directory where they have more permissions, the
permissions are correctly set to the one from the parent taget folder.

This was caused by the ObjectStoreStorage::copyFromStorage using
the jailed storage and cache entry instead of the unjailed one like other
storages (the local one).
Steps to reproduce

+ Use object storage
+ Create a groupfolder with one group having full permission and another one
  who can just read files.
+ With an user who is in the second group, copy a file from the groupfolder to
  the home folder of this user.
+ The file in the home folder of the user will be read only and can't be deleted
  even though it is in their home folder and they are the owner. In oc_filecache,
  the permissions stored for this file are 1 (READ)

Signed-off-by: Carl Schwan <carl@carlschwan.eu>