Vagrant: Prefer Parallels over VirtualBox

Having both installed on OSX, one should prefer Parallels.
Vagrant uses the first one provided working.

refs #10167

Vagrantfile

@@ -21,14 +21,6 @@ Vagrant.configure(VAGRANTFILE_API_VERSION) do |config|
 
   config.vm.provision :shell, :path => ".puppet/manifests/puppet.sh"
 
-  config.vm.provider :virtualbox do |v, override|
-    override.vm.box = "centos-71-x64-vbox"
-    override.vm.box_url = "http://boxes.icinga.org/centos-71-x64-vbox.box"
-
-    v.customize ["modifyvm", :id, "--memory", "1024"]
-    v.customize ["modifyvm", :id, "--cpus", "2"]
-  end
-
   config.vm.provider :parallels do |p, override|
     override.vm.box = "parallels/centos-7.1"
 
@@ -44,6 +36,14 @@ Vagrant.configure(VAGRANTFILE_API_VERSION) do |config|
     p.cpus = 2
   end
 
+  config.vm.provider :virtualbox do |v, override|
+    override.vm.box = "centos-71-x64-vbox"
+    override.vm.box_url = "http://boxes.icinga.org/centos-71-x64-vbox.box"
+
+    v.customize ["modifyvm", :id, "--memory", "1024"]
+    v.customize ["modifyvm", :id, "--cpus", "2"]
+  end
+
   config.vm.provision :puppet do |puppet|
     puppet.hiera_config_path = ".puppet/hiera/hiera.yaml"
     puppet.module_path = [ ".puppet/modules", ".puppet/profiles" ]

doc/vagrant.md

@@ -3,11 +3,16 @@
 ## Requirements
 
 * Vagrant >= version 1.5
-* VirtualBox or Parallels
+* VirtualBox or Parallels Desktop
 
 > **Note:** The deployment of the virtual machine is tested against Vagrant starting with version 1.5.
 > Unfortunately older versions will not work.
 
+Parallels requires the additional provider plugin
+[vagrant-paralells](http://parallels.github.io/vagrant-parallels/docs/) to be installed:
+
+    $ vagrant plugin install vagrant-parallels
+
 ## General
 
 The Icinga Web 2 project ships with a Vagrant virtual machine that integrates