This commit extends our healtcheck with an optional leader check. This
is to ensure that given network partition or other cluster wide failure
we act as soon as possible to avoid a split-brain situation where a new
leader is elected but we still hold onto our etcd client.
This commit adds a new health check, tor connection, to our liveness
monitor. A monitor refactor is applied to the server creation such that
the scope of health check creation is managed within one function.
In certain container set ups, it's useful to optionally have lnd just shutdown if it detects that its certs are expired, as assuming there's a hypervisor to restart the container/pod, then upon restart, lnd will have fully up to date certs.
Add a new health check package which will periodically poll health
check functions and shutdown if we do not succeed after our set number
of attempts. The first check that we add is one for our chain backend,
to ensure that we are connected to a bitcoin node.
