setting the correct keep alive timeouts in grpc clients to reset the idle timeouts over NLB

[aman-bansal]

This change is 

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}