Add inverted / negative condition for X-Fleet options

[kayrus]

Like it is done in systemd

With ConditionPathExists= a file existence condition is checked before a unit is started. If the specified absolute path name does not exist, the condition will fail. If the absolute path name passed to ConditionPathExists= is prefixed with an exclamation mark ("!"), the test is negated, and the unit is only started if the path does not exist.

• MachineID=!id - run globally, but not on MachineID
• MachineMetadata=!metadata - run globally, but not on machine with specified metadata

Or probably implement additional options (like Conflicts!=MachineOf):

• ConflictsMachineID
• ConflictsMachineMetadata

[pmoust]

Very interested in this.

[brandonkruse]

This would be great functionality