LU-18792 tests: fix sanity-hsm test_26e for interop testing

LU-18792 tests: fix sanity-hsm test_26e for interop testing

sanity-hsm test_26e fails in interop with 2.15.x version.
The test needs to be skipped for interop testing.

Test-Parameters: trivial
Test-Parameters: testlist=sanity serverversion=2.15.6 env=ONLY=26e
Fixes: 241cf3c6d0 ("LU-16235 hsm: get a valid cookie for RAoLU request")
Signed-off-by: Etienne AUJAMES <eaujames@ddn.com>
Change-Id: I56bafcfb2617637a88e328995aefb6ffa9785b37
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/58373
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Guillaume Courrier <guillaume.courrier@cea.fr>
Reviewed-by: Oleg Drokin <green@whamcloud.com>