validateelements: removed redundant test cases and covered more elements

Submitted by Prashant Gotarne

Link to original bug (#751027)

Description

Validateelements generates redundant test cases for element.
It is creating test case for each property with default value. Test cases for element with multiple properties with default value are the redundant test cases.
Instead of generating test case for each property with default value, generate only one test case with DEFAULT behavior.