LU-11389 lnet: increase lnet transaction timeout

LU-11389 lnet: increase lnet transaction timeout

Increase the new LNet Health transaction timeout to the original
50s value, to avoid spurious lnet-selftest failures and expected
false timeouts under load.

Fix the lnet_transaction_timeout module parameter description.

Test-Parameters: trivial clientarch=aarch64 testlist=lnet-selftest,lnet-selftest,lnet-selftest,lnet-selftest
Test-Parameters: clientarch=aarch64 testlist=lnet-selftest,lnet-selftest,lnet-selftest,lnet-selftest

Signed-off-by: Sonia Sharma <sharmaso@whamcloud.com>
Change-Id: Ic9df69ef8c7a4085815b54dc6741f37a73d36a75
Reviewed-on: https://review.whamcloud.com/33231
Tested-by: Jenkins
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: James Nunez <jnunez@whamcloud.com>
Reviewed-by: Amir Shehata <ashehata@whamcloud.com>