With slow CPU, gRPC can lag behind with RPCs being sent before
calling 'Up', returning 'no address available' on the first try.
Signed-off-by: Gyu-Ho Lee <gyuhox@gmail.com>
This commit adds a mechanism of handling a case of expired auth token
to clientv3. If a server returns an error code
grpc.codes.Unauthenticated, newRetryWrapper() tries to get a new token
and use it as an option of PerRPCCredential.
Fixes https://github.com/coreos/etcd/issues/7012