Reload consul configuration

[jorgemarey]

Attemps to fix #53.

This PR allows to reload the configuration to reload the consul values like token, certs ...
This is useful when deploying the ESM with short lived consul credentials (nomad - vault integration)

Changes:

• Intercep sighup signal to reload
• Create a lock around the client using the getClient() method so each time we use it there was a change in configuration it'll use the new client.
• Change how leader routine works. As the lock struct doesn't allow to change the client. We need to stop the lock and create it again.