Enumerate event if it has disposition or has any reference in the contact link or instrument records. #3870.

Update the tests for events when no instruments or no contact links associated. #3870.
Drop the checks for event with disposition in the contact links and instruments records. #2154.
Merge pull request #134 from NUBIC/bug_3870_2154

Bug: 3870 & 2154. Add/Update checks for enumerating events records. Drop the event checks from contact link and instrument records.