Use existing config variable, not a new one

Without this, log remained closed. Always.
Merge pull request #1253 from otoolep/fix_config_ref

Use existing config variable, not a new one
Add logging of Raft initialization
Tell Broker to join during 'join-cluster'
Add connection URL to Broker
Explicitly use 'raft' in URL path for Raft ops
Merge branch '3_node_raft' of github.com:otoolep/influxdb into 3_node_raft