Fixes https://github.com/letsencrypt/boulder/issues/1212.
This exposes a new constructor in amqp-rpc.go specifically for ActivityMonitor,
which overrides the normal routingKey to be the wildcard "#".
It also adds an expvar for the number of messages processed in ActivityMonitor,
and adds an integration test case that checks that ActivityMonitor has received
more than zero messages.
Previously our executables would all try to declare the boulder exchange on
startup, which may have been leading to some race conditions in Travis. Also,
the Activity Monitor would try to bind a queue to the exchange at startup.
In prod both of these tasks are taken care of administratively, so including
them in the app code was adding unnecessary complexity. It also may have been
part of an issue causing Activity Monitor to fail to start up recently.
Also, turn the Activity Monitor into an RPC service, which gets it reconnects
for free, and add it to startservers.py.
In the process, break out AMQP config into its own struct, one per service.
The AMQPConfig struct is included by composition in the config structs that need
it. If any given service lacks an AMQP config of its own, it gets a default
value from the top-level AMQP config struct, for deployability reasons.
Tightens the RPC code to take a specific AMQP config, not an over-broad
cmd.Config.
Shortens construction of specific RPC clients so they instatiate the generic
client connection themselves, simplifying per-service startup code.
Remove unused SetTimeout method on RPC clients.
Jacob Hoffman-Andrews
Roland Shoemaker