Changed implementation of proxy setup

Changed the setup_http_proxy method to setup_proxy.
The same arguments are used as before. This change includes
workarounds for pulp proxy configuration. However, until BZ1114083
is fixed, easier proxy support will not be possible.
The purpose of this is to grab the IP information on the local network about the proxy server IP address.
The suggestion will break on RHEL based machines, see the sample below

```python
>>> ping_result = '64 bytes from localhost (127.0.0.1): icmp_seq=1 ttl=64 time=0.054 ms'
>>> re.search('\d+ bytes from (.*):', ping_result).group(1)
'localhost (127.0.0.1)'
```