raft: infrastructire for raft integration test

[SUMUKHA-PK]

To setup a thorough raft integration test we need the following up:

• [ ] A generic integration testing framework that uses actual multiple servers. (#175 )
• [ ] A module to enable failing a server. (#176)

General thoughts:

The test must run until the user determines and must allow the servers to crash and recover gracefully whilst the cluster runs raft.