Wait to fire start event until socket is created

Previously, this check only worked if no host was specified and was
hard coded to check for "/var/run/docker.sock"

This change generalizes that check and captures any specified socket
and waits for it to be created.

Caveat: This will only check the first socket specified, but it is an
improvement over none at all.

Fixes #185160

Signed-off-by: Andrew Guenther <guenther.andrew.j@gmail.com>