Add liveness/readiness probe parameters

- PeriodSeconds - How often to probe
- SuccessThreshold - Number of successful probes to go from failure to success state
- FailureThreshold - Number of failing probes to go from success to failure state

This commit includes to changes in behavior:

1. InitialDelaySeconds now defaults to 10 seconds, rather than the
kubelet sync interval (although that also defaults to 10 seconds).
2. Prober only retries on probe error, not failure. To compensate, the
default FailureThreshold is set to the maxRetries, 3.

pkg/api/types.go

@@ -713,7 +713,8 @@ type ExecAction struct {
 	Command []string `json:"command,omitempty"`
 }
 
-// Probe describes a liveness probe to be examined to the container.
+// Probe describes a health check to be performed against a container to determine whether it is
+// alive or ready to recieve traffic.
 type Probe struct {
 	// The action taken to determine the health of a container
 	Handler `json:",inline"`
@@ -721,6 +722,13 @@ type Probe struct {
 	InitialDelaySeconds int64 `json:"initialDelaySeconds,omitempty"`
 	// Length of time before health checking times out.  In seconds.
 	TimeoutSeconds int64 `json:"timeoutSeconds,omitempty"`
+	// How often (in seconds) to perform the probe.
+	PeriodSeconds int64 `json:"periodSeconds,omitempty"`
+	// Minimum consecutive successes for the probe to be considered successful after having failed.
+	// Must be 1 for liveness.
+	SuccessThreshold int `json:"successThreshold,omitempty"`
+	// Minimum consecutive failures for the probe to be considered failed after having succeeded.
+	FailureThreshold int `json:"failureThreshold,omitempty"`
 }
 
 // PullPolicy describes a policy for if/when to pull a container image