illumos gate

beadm should remove any temporary BE activation when a BE is deleted, and should properly account for renames.

For example, here's what happens now with delete and re-create:

bloody# beadm list
BE           Active Mountpoint Space   Policy Created
20210107     NR     /          131.89G static 2021-01-07 23:59
bloody# beadm create bob
Created successfully
bloody# beadm activate -t bob
Activated successfully
bloody# beadm list
BE           Active Mountpoint Space   Policy Created
20210107     NR     /          131.89G static 2021-01-07 23:59
bob          T      -          1.92M   static 2021-01-13 12:08
bloody# beadm destroy -Ffs bob
Destroyed successfully
bloody# beadm create bob
Created successfully
bloody# beadm list
BE           Active Mountpoint Space   Policy Created
20210107     NR     /          131.89G static 2021-01-07 23:59
bob          T      -          1.75M   static 2021-01-13 12:08