changed maxentities & test fixes for jenkins jobs (ready for review)

- Updated maxentities tests 
- Changed a test that creates 1000 (default maxentities) servers to create only 26 servers. 
- Unskipped negative test for group creation with blank name
- Increased sleep time for the multiple webhooks test, as ORD jenkins job was failing
- Added delay in polling, for check_for_expected_number_of_building_servers method in fixtures