Update GoCloud to v0.21.1+
This dependency update is the first step to supporting Azure Managed Identities (gitlab#242245) so that static credentials are not needed. This is equivalent to Amazon's IAM instance profile.
This GoCloud update also requires a newer gprc-go version. v1.34.1 fixes a UNIX socket dialing issue that was broken in v1.34.0: https://github.com/grpc/grpc-go/issues/3990
Part of gitlab#242245
Edited by Stan Hu