Starting an exec can take a significant amount of time while under heavy
container operation load. In extreme cases the time to start the process
can take upwards of a second, which is a significant fraction of the
default health probe timeout (30s). With a shorter timeout, the exec
start delay could make the difference between a successful probe and a
probe timeout! Mitigate the impact of excessive exec start latencies by
only starting the probe timeout timer after the exec'ed process has
started.
Add a metric to sample the latency of starting health-check exec probes.
Signed-off-by: Cory Snider <csnider@mirantis.com>
