Added category RegressionTests to test cases related to Defects verification.

As a part of my task MAGN-4384, I am marking these tests as RegressionTests.
Few more tests marked under category RegressionTests which was left because they were added in different classes/projects.
By mistake added Regression as a category so changing back to RegressionTests
Merge pull request #2279 from riteshchandawar/CategoryRegressionTests

Added category RegressionTests to test cases related to Defects verification