Add suport for vagrant-hostmanager to manage /etc/hosts

At the moment the used hostnames in the configuration file are
maybe not resolvable on the Vagrant instances which will result
in issues (for example the SERVICE_HOST variable in local.conf
used the hostname of the manager node).

The vagrant-hostmanager plugin manages the /etc/hosts file
and will set correct entries there to make the hostnames in the
configuration file resolvable.

Change-Id: I7ecd379c9f7e47c04abc85aa61de9c6c50f8a50b

README.md

@@ -38,6 +38,10 @@ have enough horsepower you should make the file something like:
 You can probably get away with less cpus, and 4096 MB of memory, but
 the above is recommended size.
 
+If the used hostnames in the ``config.yaml`` file (variable ``hostname_manager``
+and ``hostname_compute``) are not resolvable you have to install the
+``vagrant-hostmanager`` plugin (``vagrant plugin install vagrant-hostmanager``).
+
 
 Local Setup
 --------------------

Vagrantfile

@@ -89,6 +89,13 @@ Vagrant.configure(VAGRANTFILE_API_VERSION) do |config|
   #                https://github.com/mitchellh/vagrant/issues/1673
   config.ssh.shell = "bash -c 'BASH_ENV=/etc/profile exec bash'"
 
+  if Vagrant.has_plugin?("vagrant-hostmanager")
+    config.hostmanager.enabled = true
+    config.hostmanager.manage_host = true
+    config.hostmanager.ignore_private_ip = false
+    config.hostmanager.include_offline = true
+  end
+
   config.vm.define "manager" do |manager|
     configure_vm("manager", manager.vm, conf)
     manager.vm.network "forwarded_port", guest: 80, host: 8080, host_ip: "127.0.0.1"