Changes made for arch, OS, media, domain, partition table, subnet and roles modules

Changes made for arch, OS, media, domain, partition table, subnet and roles modules
- Added a function (_configure_xxx) to remove the duplication of code under create and update functions
- Since every single test requires object creation so added a create helper function in all test modules like `create_os` for OS, `create_domain` for domain and `create_medium` for Medium respectively.  
- Added exceptions wherever required in above all modules
- Updated variables like oldname to old_name
- Updated all single quote docstrings to """docstrings"""
- Updated OS tests, replace the os_name from Redhat to 'Red Hat'
- Added assertion to validate tests results