e2e: add PollInterval()

Various different tests all have their own poll intervals. As a start towards
consolidating that, the interval from test/e2e/framework/pod (as one of the
most common cases for polling) is moved into the framework.

Changing other helper packages and tests needs to follow.

test/e2e/framework/timeouts.go

@@ -19,6 +19,7 @@ package framework
 import "time"
 
 var defaultTimeouts = TimeoutContext{
+	Poll:                      2 * time.Second, // from the former e2e/framework/pod poll interval
 	PodStart:                  5 * time.Minute,
 	PodStartShort:             2 * time.Minute,
 	PodStartSlow:              15 * time.Minute,
@@ -42,6 +43,9 @@ var defaultTimeouts = TimeoutContext{
 
 // TimeoutContext contains timeout settings for several actions.
 type TimeoutContext struct {
+	// Poll is how long to wait between API calls when waiting for some condition.
+	Poll time.Duration
+
 	// PodStart is how long to wait for the pod to be started.
 	PodStart time.Duration
 
@@ -111,3 +115,9 @@ func NewTimeoutContext() *TimeoutContext {
 	copy := TestContext.timeouts
 	return &copy
 }
+
+// PollInterval defines how long to wait between API server queries while
+// waiting for some condition.
+func PollInterval() time.Duration {
+	return TestContext.timeouts.Poll
+}