[Sailee/Priti]:Modified LoanProductTestBuilder in Integration tests to support minPrincipal and maxPrincipal fields

Modified LoanProductTestBuilder in Integration tests to support minPrincipal and maxPrincipal fields for LoanProduct

Fields "minPrincipal" and "maxPrincipal" were added to createLoanProduct API as mandatory fields. So,corresponding changes are made in the integration tests to support the same.

P.S: Kindly run the Integration tests using "gradle integrationTest" before checking in API code changes.