LU-17571 tests: set idle_timeout in sanity 77l, 812[ab], 816

LU-17571 tests: set idle_timeout in sanity 77l, 812[ab], 816

sanity.sh:test_77l,812a,812b,816 rely on idle_timeout set to not
0. Have the tests to take care of that.

Test-Parameters: trivial
HPE-bug-id: LUS-10951
Signed-off-by: Vladimir Saveliev <vladimir.saveliev@hpe.com>
Change-Id: I6c0cf3e7264263221b5ec54292673868f4bda25c
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/54123
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Alex Zhuravlev <bzzz@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>