remove requirement for VLAN Id to be set (fixes #126)

[nathwill]

• [x] remove requirement for VLAN id (and other required properties so stub resources can be used to manage system-provided units without mock data)
• [x] update platform versions for test suites
• [x] fix FC108 for binfmt, sysuser resources
• [x] remove nspawn workaround for older fedora version in test suite
• [x] add nspawn workaround for too-small debian machines.raw loopback volume in test suite