Communicate relevantEvents=0 for packages excluded from whitelist

Together with checking isObservableEventType this will result in a11y events
not being generated for packages that are excluded form a11y-service(s)
package whitelist

Test: cts-tradefed run singleCommand cts -d --module CtsAccessibilityServiceTestCases
Change-Id: Id65607aaccc7af7d870d009d609917ff3c6d0712