FALCON-2304 SchedulerServiceTest.testDeRegistration test fails

[pravin-dsilva]

The test fails with

java.lang.AssertionError: expected:<1> but was:<null>
	at org.testng.Assert.fail(Assert.java:89)
	at org.testng.Assert.failNotEquals(Assert.java:489)
	at org.testng.Assert.assertEquals(Assert.java:118)
	at org.testng.Assert.assertEquals(Assert.java:160)
	at org.apache.falcon.notification.service.SchedulerServiceTest.testDeRegistration(SchedulerServiceTest.java:274)

The test passed by increasing the timeout.

[Prajyot-Parab]

@pallavi-rao Have raised a new PR - https://github.com/apache/falcon/pull/416 with waitFor implementation to fix the issue.