Fix the gRPC client dialer not using the timeout passed by the
containerd client timeout option.
Commit 63b4688175 replaced the usage of deprecated `grpc.DialContext`
with `grpc.NewClient`.
However, the `dialer.ContextDialer` relied on the context deadline to
propagate the timeout:
388fb336b0/vendor/google.golang.org/grpc/clientconn.go (L216)
This assumption is now broken, because `grpc.NewClient` doesn't do any
initial connection and defers it to the first RPC usage.
This commit passes the timeout via the `MinConnectTimeout` grpc
connection param, which will be applied to **every** connection attempt
(not just the first).
Signed-off-by: Paweł Gronowski <pawel.gronowski@docker.com>
6b5efba83b