LU-18357 test: fix sanity-sec 27a interop with long fileset

LU-18357 test: fix sanity-sec 27a interop with long fileset

The fileset length in sanity-sec 27a was signficantly increased to
test multiple fileset fragments on the IAM. This long fileset is also
used in interop with "lctl set_param -P" with older servers instead of
"lctl nodemap_set_fileset".

However, running "lctl get_param" with this long fileset on older
servers (<=2.15) causes a line break (due to the output being longer
than 80 characters) which results in "wait_nm_sync" to fail when
comparing the expected vs. the actual output.

This patch modifies sanity-sec test 27a and reverts the fileset to its
original much shorter path in the interop case when "lctl set_param
-P" must be used. When "lctl nodemap_set_fileset" is used, the long
fileset is still set to test multiple fileset fragments.

Test-Parameters: trivial testlist=sanity-sec
Test-Parameters: trivial testlist=sanity-sec serverversion=2.15
Fixes: da3536da22ab ("LU-18357 ptlrpc: Use nodemap IAM for persisting filesets")
Signed-off-by: Marc Vef <mvef@whamcloud.com>
Change-Id: Ie1d39f3f986675133fd9d4c294e7af186f2ed1b9
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/58436
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Sebastien Buisson <sbuisson@ddn.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>