engine: Fix ValidationResult

1. Changed equals not to use instanceof since the class is final.
2. Added variable replacements to the TSEHC (toString/equals/hashCode)
   methods since it's part of the object's identity.

Change-Id: I6faefd9926c241055fc4957ce3c639308ef5833f
Signed-off-by: Mike Kolesnik <mkolesni@redhat.com>