Revert to Alpine 3.11.2.
Revert to Alpine 3.11.2.

See also: https://github.com/gliderlabs/docker-alpine/issues/539 and
https://github.com/grpc/grpc-go/issues/3572.

brocaar/lora-semtech-bridge,brocaar/lora-semtech-bridge,brocaar/lora-gateway-bridge,brocaar/lora-gateway-bridge