Fix /etc/hosts issues on rabbit servers when using FQDN

Rabbit occassionally fails to start because it can't resolve its "short
name"

The /etc/hosts file is dropped after the install phase, which starts up
rabbit automatically - Moving the /etc/hosts file correction to happen
before the install phase will resolve this.

Fixes #39
Merge pull request #40 from andymcc/rabbit_fqdn

Fix /etc/hosts issues on rabbit servers when using FQDN