LU-17735 tests: extend health check to avoid spurious failures

LU-17735 tests: extend health check to avoid spurious failures

Increase network check timeout to avoid spurious failures of tests
like sanity test 7b.  5 seconds is too short in certain environments.

Signed-off-by: Srikanth Ramamurthy <srramamu@microsoft.com>
Change-Id: Iea49f4f66efbfe0afa56ec81eadea6d792cab55f
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/54765
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Timothy Day <timday@amazon.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>