kv: Hack around GRPC context leak
kv: Hack around GRPC context leak

I believe this will prevent the leak described in
https://github.com/grpc/grpc-go/issues/888

vaibhavarora/cockroach,maxlang/cockroach,vaibhavarora/cockroach,maxlang/cockroach,vaibhavarora/cockroach,petermattis/cockroach,veteranlu/cockroach,cockroachdb/cockroach,vaibhavarora/cockroach,maxlang/cockroach,veteranlu/cockroach,paperstreet/cockroach,paperstreet/cockroach,cockroachdb/cockroach,glycerine/cockroach,maxlang/cockroach,paperstreet/cockroach,cockroachdb/cockroach,veteranlu/cockroach,veteranlu/cockroach,veteranlu/cockroach,cockroachdb/cockroach,petermattis/cockroach,paperstreet/cockroach,maxlang/cockroach,vaibhavarora/cockroach,cockroachdb/cockroach,petermattis/cockroach,paperstreet/cockroach,petermattis/cockroach,paperstreet/cockroach,vaibhavarora/cockroach,cockroachdb/cockroach,glycerine/cockroach,veteranlu/cockroach,glycerine/cockroach,glycerine/cockroach,cockroachdb/cockroach,paperstreet/cockroach,veteranlu/cockroach,maxlang/cockroach,veteranlu/cockroach,glycerine/cockroach,maxlang/cockroach,petermattis/cockroach,paperstreet/cockroach,cockroachdb/cockroach,glycerine/cockroach,glycerine/cockroach,petermattis/cockroach,glycerine/cockroach,petermattis/cockroach,vaibhavarora/cockroach,maxlang/cockroach,petermattis/cockroach,vaibhavarora/cockroach