need clear logging when server goes down for code update

[lloyd]

generally whenever the process goes down, we need clear output in the log so we know why.

[lloyd]

NOTE, winston is async, so logger.warn() followed by process.exit() will cause the process to exit before the log message is emitted. This is why we're not seeing log messages at the moment.

[jbonacci]

Verified the following in verifier.log:
...etc...
{"level":"warn","message":"code updated. closing 1 connections and shutting down."}
{"level":"info","message":"graceful shutdown complete..."}
{"level":"debug","message":"pre-seeded public key cache with key for diresworb.org"}
{"level":"info","message":"verifier server starting up"}
{"level":"debug","message":"attempting to fetching public key for diresworb.org"}
{"level":"debug","message":"public key for diresworb.org returned from cache"}
...etc...

Verified the following in keysigner.log:
...etc...
{"level":"info","message":"running on http://127.0.0.1:62600"}
{"level":"info","message":"process type is keysigner"}
{"level":"warn","message":"code updated. closing 1 connections and shutting down."}
{"level":"info","message":"graceful shutdown complete..."}
...etc...

Verified the following in browserid.log:
...etc...
{"level":"warn","message":"code updated. closing 1 connections and shutting down."}
{"level":"debug","message":"closing database connection"}
{"level":"info","message":"graceful shutdown complete..."}
{"level":"info","message":"delivering email via SMTP host: smtp.socketlabs.com"}
{"level":"info","message":"authenticating to email host as morgamic"}
{"level":"info","message":"browserid server starting up"}
{"level":"info","message":"running on http://127.0.0.1:62700"}
...etc...