Merge pull request #2718 from Varying-Vagrant-Vagrants/fix/parallels-docker-detection

Improve docker/parallels detection

Author: tomjn

Vagrantfile

@@ -42,17 +42,13 @@ end
 
 
 def vvv_is_docker_present()
-  VagrantPlugins::DockerProvider::Driver.new.execute("docker", "version")
-  return true
-rescue Vagrant::Errors::CommandUnavailable
-  return false
+  if `docker version`
+    return true
+  end
 end
 
 def vvv_is_parallels_present()
-  VagrantPlugins::DockerProvider::Driver.new.execute("prctl", "version")
-  return true
-rescue Vagrant::Errors::CommandUnavailable
-  return false
+  return Vagrant.has_plugin?("vagrant-parallels")
 end
 
 vagrant_dir = __dir__
@@ -348,7 +344,7 @@ if show_logo
   when 'hyperv'
     provider_version = 'n/a'
   when 'docker'
-    provider_version = VagrantPlugins::DockerProvider::Driver.new.execute("docker", "-v").gsub("Docker version ", "")
+    provider_version = `docker -v`.gsub("Docker version ", "")
   else
     provider_version = '??'
   end