This change introduces the new configuration option to limit number
of storlet containers running on a single now. This helps operators
avoid some nodes from being unevenly loaded.
To search storlet containers, The new container label,
managed=by=storlets
is added to all storlet containers. This allows users to run additional
containers on a same node and exclude these containers from the limit.
Change-Id: I148fa5793c19e8f894b8cb3ccecf75b3d15fb17a
a3583b598b