Watch error alert

kube-apiserver has a histogram etcd_request_duration_seconds that
measures latency between the kube-apiserver and etcd instance.
This metrics is currently dropped by cluster-prometheus. Enable
this metrics so we have visibility into etcd latency.

We ensured that this does not enable other unwanted metrcis

count by(name) ({name=~"etcd_request.+"})

etcd_request_duration_seconds_bucket
etcd_request_duration_seconds_count
etcd_request_duration_seconds_sum

Previously the alert would fire when the number of Alertmanager pods
didn't match the number of replicas defined in the Alertmanager spec
even though all the running pods had the same configuration hash. This
type of issue is already covered by KubeStatefulSetUpdateNotRolledOut
(and possibly KubePodNotReady), having AlertmanagerConfigInconsistent
also active in this situation creates unnecessary noise.

With this change, the alert expression only returns when Alertmanager
pods have different configuration hash values irrespective of the number
of pod replicas. The message annotation has also been enhanced to report
the configuration hash for each pod.

Signed-off-by: Simon Pasquier <spasquie@redhat.com>

v0.40

The ignored filesystem types now matches the default, so the
comment and arg can be removed.

Ignore kubelet pod filesystem mounts of the form:
/var/lib/kubelet/pods/1b260ce7-e75d-44d4-8409-922d2bd0851f/volumes...
Metrics for these volumes are available via the kubelet_volume_stats*
metrics.

This reverts commit cdaaf3d5.

Signed-off-by: Benjamin <benjamin@yunify.com>

use $._config.namespace instead of hard-coding 'monitoring'

Fixes #455.