Do nextboot -D twice during boot.  The first time in rc.d/root which ensures that we can remove the file as early as possible, but shut up nextboot at this moment if the operation is failed, because /boot is not necessarily a part of /; the newly added second run is placed in rc.d/mountlate after all filesystems were mounted.
Do nextboot -D twice during boot.  The first time in rc.d/root which ensures that
we can remove the file as early as possible, but shut up nextboot at this moment
if the operation is failed, because /boot is not necessarily a part of /; the
newly added second run is placed in rc.d/mountlate after all filesystems were
mounted.

Discussed at:		-rc@
Suggestions from:	brooks, mtm
MFC after:		1 month

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