[Bug] DatabasePresenceVerifier not working for booleans in the additional conditions #3927 

Change comparison operator from 'Equal' to 'Identical' when comparing value to 'NULL'/'NOT_NULL', so a comparison with a boolean value returns correct result.
Merge pull request #3928 from lpopov/4.1

[Bug] DatabasePresenceVerifier not working for booleans in the additional conditions #3927
Fix tabs.
Merge branch '4.1'