test(pillar): use disable_mlock for FreeBSD (Vagrant)

Service wasn't starting without this being resolved.

Author: myii

test/salt/pillar/prod_server.sls

@@ -6,6 +6,10 @@ vault:
     storage:
       file:
         path: /var/lib/vault/data
+    # `disable_mlock` is only needed for FreeBSD (Vagrant)
+    # Doesn't appear to cause a problem for other instances but use an `if`
+    # block if it does
+    disable_mlock: true
   tls_disable: 1
   self_signed_cert:
     enabled: true