Changed TraceKey/StartTimeKey/TokenFieldNameGRPCKey to struct{} to
follow the correct usage of context. Similar patch to #8901.
Signed-off-by: Wei Fu <fuweid89@gmail.com>
Streams are now closed after being used in the lessor `keepAliveOnce` method.
This prevents the "failed to receive lease keepalive request from gRPC stream"
message from being logged by the server after the context is cancelled by the
client.
Signed-off-by: Justin Kolberg <amd.prophet@gmail.com>