Added etcd hosts failover.

[cloakedcode]

Allows multiple etcd nodes to be configured and rotates through until it successfully establishes a connection.

[philips]

lgtm

[igor47]

hi @cloakedcode ; this PR needs a rebase now that #68 has been merged. also, i would not merge this because it breaks backwards compatibility of existing config files.

can you rework this to add etcd_hosts as a secondary parameter but still also accept the old host and port options? then you can just add what's in host and port to hosts and loop through all of them.

[telmich]

Hey! This looks very interesting! Is there any work going on in this issue?