Close client connections to domain to be removed; verify the config file

Now all the client connections associated with a domain to be removed
are closed. Additionally, a config file on each node is compared to the
one on the initiating node.

The whole cluster reload mechanism works as follows:
1. Parse the configuration file on the initiating node.
2. Compute a diff between current configuration and the one read from
   the provided file
3. Compute a hash of the current node's configuration (config version)
4. Compute a hash of the new configuration read from file (file version)
5. Apply new configuration on the current node
6. Send configuration diff computed on the initiating node to other nodes
   along with the config version, file version and the file path
7. Compute config version and file version (after parsing it) on the
   other nodes and verify that they match their counterparts from
   the initiating node; if any doesn't match cancel the operation
8. Apply the configuration diff on the other nodes