Documentation/etcd-mixin/mixin.libsonnet: Add alerts for etcd fsync duration
Documentation/etcd-mixin/mixin.libsonnet: Add alerts for etcd fsync duration

This commit adds support to check the 99th percentile of the etcd
members fsync duration and fires a critical alert when it is greater
than 1 sec. The recommended fsync for etcd is 20 ms but there might
be scenarios where a user might be using bad disks for reasons. This
will make sure to let the user/admin know that it is critical for
etcd performance.

ajityagaty/etcd,mkumatag/etcd,mqliang/etcd,gyuho/etcd,mkumatag/etcd,li-ang/etcd,mqliang/etcd,gyuho/etcd,rnaveiras/etcd,ajityagaty/etcd,ajityagaty/etcd,rnaveiras/etcd,coreos/etcd,etcd-io/etcd,rnaveiras/etcd,etcd-io/etcd,mqliang/etcd,coreos/etcd,mkumatag/etcd,li-ang/etcd,etcd-io/etcd