public SimpleHttpSource ensureReady() {
		return ensureReady(2000);
	}
Ensure that the source is ready to take requests by sending http header requests to the source for up to 2
seconds.

@throws IllegalStateException if can't connect to the source within the given timeout.
spring-xd-test-fixtures/src/main/java/org/springframework/xd/test/fixtures/SimpleHttpSource.java