This commit fix random issues found with functionnal tests where the client
was refuse by the storage, because the latter was not fully initialized,
but never tried to reconnect to it if no other storages were available.

The main change introoduced is the availability of 'iterateForObject'
method on ConnectionPool. It allow iterate over potential node connections
for a given object id with the ability of waiting for the node to be ready
if not. It includes the common pattern that retreive the cell list,
randomize then sort them and never returns a None value, which suppose that
the outer loop must check if at least one iteration happens, for example.

Also included:
- getPartitionTable is now private because the connection needs it
- Deletion of _getCellListFor*
- Fixed tests
- New tests for ConnectionPool.iterateForObject

git-svn-id: https://svn.erp5.org/repos/neo/trunk@2578 71dcc9de-d417-0410-9af5-da40c76e7ee4