LU-15447 tests: sanity-flr/208 reset rotational status

LU-15447 tests: sanity-flr/208 reset rotational status

new kernels (e.g. 4.18.0-305.25.1) declares loopback devices
in tmpfs as non-rotational one. sanity-flr/208 does wrong
assumption that devices are non-rotational by default. thus,
sanity-flr/208 started to fail with new kernels.

Fixes: 8507472dd37e ("LU-14996 lov: prefer mirrors on non-rotational OSTs")
Signed-off-by: Alex Zhuravlev <bzzz@whamcloud.com>
Change-Id: Ib5c42da39667227a6cff5d379e30d2cd6c1e2773
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/46088
Reviewed-by: Colin Faber <cfaber@ddn.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>