Signed-off-by: Peng Tao <bergwolf@gmail.com>

URL format is <scheme>://<host>[:port]/<path>, while gRPC name syntax
is <scheme>://<authority>/<endpoint_name>.

Also if a unempty scheme is not supported by gRPC, gRPC ignores all the
remaining part of the address and just pass an empty string to the
dialer.

Therefore we handcraft a self-defined vsock format
vsock:<cid>:<port> to bypass gRPC parsing and let the vsock dialer parse
the vsock gRPC address.

Then we provide URL format based address interface to NewAgentClient() callers.

Also add a few address tests to make sure this works.

Signed-off-by: Peng Tao <bergwolf@gmail.com>

Signed-off-by: Peng Tao <bergwolf@gmail.com>

This is the first commit related to the vendoring of all dependencies.
This will prevent from any breakage in case a dependency would break
the backward compatibility.

Fixes kata-containers#32

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>