Allow for disabling audio on vagrant via env var

With bluetooth headphones, Vagrant/VirtualBox coming up with audio enabled causes the headphone to switch profiles from A2DP to HSP, causing poor audio quality if you're listening to music while working on your Ansible roles. The easiest way to work around this is to simply disable audio on the VMs. This PR disables audio on vagrant VMs if the MOLECULE_VAGRANT_DISABLE_AUDIO environment variable is set.

{{cookiecutter.role_name}}/molecule/default/create.yml

@@ -22,7 +22,7 @@
         provider_memory: "{{ item.memory | default(omit) }}"
         provider_cpus: "{{ item.cpus | default(omit) }}"
         provider_options: "{{ item.provider_options | default(omit) }}"
-        provider_raw_config_args: "{{ item.provider_raw_config_args | default(omit) }}"
+        provider_raw_config_args: "{{ (item.provider_raw_config_args | default([])) + ([ \"customize ['modifyvm', :id, '--audio', 'none']\" ] if lookup('env', 'MOLECULE_VAGRANT_DISABLE_AUDIO') | bool else []) }}"
 
         provision: "{{ item.provision | default(omit) }}"