remove hardcoded upgrade_to and upgrade_version as we will pass it from testDB

Change-Id: I8379cd6f10b68ffbef3dea741e937f188364eed8
Reviewed-on: https://review.couchbase.org/c/testrunner/+/244282
Reviewed-by: Saimirra R <saimirra.r@couchbase.com>
Tested-by: Balakumaran G <balakumaran.gopal@couchbase.com>
Reviewed-by: Balakumaran G <balakumaran.gopal@couchbase.com>

Author: bkumaran