K 10
svn:author
V 6
kevans
K 8
svn:date
V 27
2019-02-10T21:19:09.114311Z
K 7
svn:log
V 546
libbe(3): Add a destroy option for removing the origin

Currently origin snapshots are left behind when a BE is destroyed, whether
it was an auto-created snapshot or explicitly specified via, for example,
`bectl create -e be@mysnap ...`.

Removing it automatically could be argued as a POLA violation in some
circumstances, so provide a flag to be_destroy for it. An accompanying
option will be added to bectl(8) to utilize this.

Some minor style/consistency nits in the affected areas also addressed.

Reported by:	Shawn Webb
MFC after:	1 week

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