LU-10632 tests: recovery-small test_26 idle_timeout

LU-10632 tests: recovery-small test_26 idle_timeout

In recovery-small test_26() use "lfs df" instead of plain "df"
since statfs may be fetched from the MDS cache and will not
ensure that the client->OST connections are currently active.

Also, check a few entries further back in the OSC state log for an
EVICTED message, in case the client idle disconnects from the server
again while checking all of the imports.

Lustre-change: https://review.whamcloud.com/42006
Lustre-commit: b4391fcdaf392a50bd1419342eca3b730c077ed2

Test-Parameters: trivial testlist=recovery-small env=ONLY=26a,ONLY_REPEAT=100

Fixes: 5a6ceb664f07 ("LU-7236 ptlrpc: idle connections can disconnect")

Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: I8c370cb75f4e06258ef3c032630fc20354a15dcc
Reviewed-by: Alex Zhuravlev <bzzz@whamcloud.com>
Reviewed-by: James Nunez <jnunez@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/43237
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>