Update README_docker_io.md

[pedrorsantana]

trafficstars

Fix image names in Docker run commands README to include "hashicorp/" prefix to make sure that local trash images will not pollute the process.

Scenarios of Errors: ` $ docker run
--network host
-e 'BOUNDARY_POSTGRES_URL=postgresql://postgres:[email protected]:5432/postgres?sslmode=disable'
boundary database init -config /boundary/config.hcl

Unable to find image 'boundary:latest' locally docker: Error response from daemon: pull access denied for boundary, repository does not exist or may require 'docker login': denied: requested access to the resource is denied. See 'docker run --help'. `