Changed testcase 'test_send_on_vm_change' to test vm change

This patch changed the test case
NotificationsTestCase.test_send_on_vm_change to test the
vm change instead of the task change

Change-Id: I244c5eca5b5b2a254b14126d92e020f072714ade
Closes-bug: #1397247
Merge "Changed testcase 'test_send_on_vm_change' to test vm change"