conan Unable to connect to conan-center=https://conan.bintray.com

## Problem

Using the docker container for the training, while using the command `conan install ..` mentioned in [this lesson](https://academy.jfrog.com/conan-essentials/583095) conan can not reach conan center remote.

This is caused when the container produces `/etc/resolv.conf` contains the localhost address `nameserver 127.0.X.X`.

### Suggested Enhancement

This can be fixed by filling `/etc/resolv.conf` with a public DNS like google's public DNS `8.8.8.8` while building the container.

### Details about the environment used:

- VirtualBox
- Guest: Ubuntu 18.04
- Host: Windows 10

### Exact error output

```bash
ERROR: HTTPSConnectionPool(host='conan.bintray.com', port=443): Max retries exceeded with url: /v1/ping (Caused by NewConnectionError(': Failed to establish a new connection: [Errno -3] Temporary failure in name resolution'))

Unable to connect to conan-center=https://conan.bintray.com
1. Make sure the remote is reachable or,
2. Disable it by using conan remote disable,
Then try again.
```

Start by reproducing `conan install ..` in the Docker training container and inspect `/etc/resolv.conf`, especially the localhost nameserver shown in the report. Confirm the container can resolve and reach conan-center, with completion indicated by the command succeeding instead of producing the reported name-resolution error.

Written by the indexing model from the issue text.