Disable gRPC service config TXT DNS record lookup (#205)
Disable gRPC service config TXT DNS record lookup (#205)

The kiam server doesn't publish a gRPC service configuration in DNS,
and the CoreDNS server used commonly in Kubernetes doesn't serve these
records anyway, so disable this behavior in the kiam agent's gRPC
client.

Fixes #204.
uswitch/kiam,uswitch/kiam