LU-16356 tests: add trap 0 in cleanup_echo_devs

LU-16356 tests: add trap 0 in cleanup_echo_devs

"trap 0" was accidentally removed from cleanup_echo_devs
in "LU-16356 hsm: store crh in rhashtable instead of list".
Add it back.

Test-Parameters: trivial
Fixes: dc13a56187 ("LU-16356 hsm: store crh in rhashtable instead of list")
Signed-off-by: Sergey Cheremencev <scherementsev@ddn.com>
Change-Id: I5d309a926f376165aacc8f0fe1c3b04dcd86f545
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/54183
Reviewed-by: Alex Zhuravlev <bzzz@whamcloud.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>