Circular dependencies in actions with ActionAddMember

[vojtechtrefny]

When using the ActionAddMember and ActionRemoveMember it's easy to create a dependency cycle when adding more actions:

1. Resize a LV.
2. Create new PV partition.
3. Add the PV to the VG.
4. Blivet fails with blivet.tsort.CyclicGraphError: graph contains cycles

The problem is that both the ActionCreateDevice and ActionCreateFormat for the new PV depend on the resize action (which it shouldn't) of the LV which depends on the ActionAddMember (which is correct, the LV resize might need the extra space added by the new PV) which depends on the PV create action (again correct) creating the cycle.

The problem is that all create actions depend on all actions with higher type (e.g. resize) even if these actions are on devices that don't depend on each other.

blivet/blivet/deviceaction.py

Lines 302 to 305 in 620685c

	def requires(self, action):
	""" Return True if self requires action. """
	return (not (self.is_container or action.is_container) and
	self.type < action.type)