Add new tests that check that ignore-unused-resources works as expected in combination with --backup:

• check that if ignore-unused-resources is undefined and --backup not set, then the behavior is as if the attribute had a value of 'true'
• check that if ignore-unused-resources is undefined and --backup is set, then the behavior is as if the attribute had a value of 'false'
• no need to check that if ignore-unused-resources is true and --backup not set, this is already covered by other tests
• check that if ignore-unused-resources is true and --backup is set, slave does not have full domain config
• check that if ignore-unused-resources is false and --backup not set, then the slave has full domain config
• check that if ignore-unused-resources is false and --backup is set, then the slave has full domain config