LU-16125 tests: make sanity-sec more robust with SSK

LU-16125 tests: make sanity-sec more robust with SSK

Encryption related tests in sanity-sec carry out unmount and mount of
clients in order to exercise code with and without the encryption key.
In case SSK is in use, we need to make sure flavors are properly
applied before carrying on.

Signed-off-by: Sebastien Buisson <sbuisson@ddn.com>
Change-Id: I92e85dc6dcef43f70a7fe05db94cd18fe66a3a24
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/48386
Reviewed-by: Zhenyu Xu <bobijam@hotmail.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>