UnitPath= is also writable via native units and may be used by generators to clarify from which file a unit is generated. This patch also hooks up the cryptsetup and fstab generators to set UnitPath= accordingly.
This makes all generators log to kmsg by default.
Bit by bit we should remove non-unit parsing from PID 1 and move into generators, to clean up our code base a bit and clearly separate parsers.