tests - create domain from existing image and same domainUID in different ns (#1586)

* test to add a second domain using the image as the first one

* refactoring and also adding test for same domainUID in different ns

* refactoring the test

* removing the readSecret calls and refactoring the test

* remove empty lines

* fixing after review comments

* more updates after review comments

Co-authored-by: [email protected] <[email protected]>

Author: bhavaniravichandran