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.
@elyezer, the `-n` option prevents name resolution. Does that output you gave occur even when `-n` is given? That example doesn't jive with what I get.

```
[ichimonji10@beech:~]$ ping -c 1 -n localhost | grep icmp_seq
64 bytes from 127.0.0.1: icmp_seq=1 ttl=64 time=0.038 ms
```