LU-15611 osd-zfs: Cleanup while mount failed

LU-15611 osd-zfs: Cleanup while mount failed

Need clean up in error out path in osd-zfs.

Signed-off-by: Yang Sheng <ys@whamcloud.com>
Change-Id: I47d9ee9483acb8e1d60c77e8cfc481902a1535ac
Reviewed-on: https://review.whamcloud.com/46678
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Emoly Liu <emoly@whamcloud.com>
Tested-by: Emoly Liu <emoly@whamcloud.com>
Reviewed-by: Alex Zhuravlev <bzzz@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>