integ-cli: skip test assuming -H is unix://...

`TestCliProxyDisableProxyUnixSock` verifies that HTTP_PROXY env var is
used when DOCKER_HOST is not set and cli connects to `unix://...` by
default.

In the windows/darwin CLI CIs, daemon is on remote host and we always
connect via `tcp://`, therefore this test fails very straight. Skipping
this test to run only on "same host daemon" assumption.

Signed-off-by: Ahmet Alp Balkan <ahmetalpbalkan@gmail.com>