LU-11022 lfs: remove mirror by pool name
lfs mirror split --pool <poolname> <file>
This patch is back-ported from the following one:
Lustre-commit:
0c710a46cfb43366dc57ff6e83e414086b1d0e6c
Lustre-change: https://review.whamcloud.com/35329
Change-Id: I012e68729b94657236ba3fc530fc7b7485529ed2
Signed-off-by: Alex Zhuravlev <bzzz@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/36194
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>