Improve ZFS exporting functionality, only export pools which are on a specific device we happen to be writing to. This fixes an issue when running pc-sysinstall on a running system which needs ZFS and the main disk gets exported.
Improve ZFS exporting functionality, only export pools which are on a
specific device we happen to be writing to. This fixes an issue when
running pc-sysinstall on a running system which needs ZFS and the main
disk gets exported.

Submitted by:	kris
Obtained from:	PC-BSD

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