LU-14204 tests: make sure we have a single import

LU-14204 tests: make sure we have a single import

In sanity, retrieve the exact name of the import being used on the
client, in order to properly get information such as lock_count
or lru_size.

Lustre-change: https://review.whamcloud.com/41758
Lustre-commit: 9bbc45d3f48acf79a1ad0a1161af832e040ee52f

Lustre-change: https://review.whamcloud.com/42019
Lustre-commit: 4541d5424ebcac028864f454af0e650f8ee9468b

Change-Id: I065b7da7990c7171d5baa24f3400c5f8ffc12fc9
Test-Parameters: trivial
Test-Parameters: env=SHARED_KEY=true testlist=sanity
Signed-off-by: Sebastien Buisson <sbuisson@ddn.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: James Nunez <jnunez@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/41855
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>