LU-12836 osd-zfs: Catch all ZFS pool change events

LU-12836 osd-zfs: Catch all ZFS pool change events

This change adds the following symlinks:

  vdev_attach-lustre -> statechange-lustre.sh
  vdev_remove-lustre -> statechange-lustre.sh
  vdev_clear-lustre -> statechange-lustre.sh

This makes it so the statechange-lustre.sh script is also called on
all ZFS events that could change the pool state.

Lustre-change: https://review.whamcloud.com/43552
Lustre-commit: e11a47da71a2e2482e4c4cf582d663cd76a2ecab

Test-Parameters: fortestonly
Signed-off-by: Tony Hutter <hutter2@llnl.gov>
Change-Id: I18edc86749e8ab91bb45f21aafd3fd47e78cbaef
Reviewed-by: Olaf Faaland-LLNL <faaland1@llnl.gov>
Reviewed-by: Nathaniel Clark <nclark@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Signed-off-by: Gian-Carlo DeFazio <defazio1@llnl.gov>
Reviewed-on: https://review.whamcloud.com/44171
Tested-by: jenkins <devops@whamcloud.com>