Support provider URI per machine definition (#1363)

Save the variables on the instance to allow for different connection
settings to be specified on a per machine basis.

Provide some rudimentary tests that ensure that the different URIs are
used when constructing connections, and additionally the connection is
created only once, no matter how many times it is subsequently called.

Fixes: #1358

spec/unit/driver_spec.rb

@@ -0,0 +1,83 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+require 'support/sharedcontext'
+
+require 'vagrant-libvirt/driver'
+
+describe VagrantPlugins::ProviderLibvirt::Driver do
+  include_context 'unit'
+
+  let(:vagrantfile) do
+    <<-EOF
+    Vagrant.configure('2') do |config|
+      config.vm.define :test1 do |node|
+        node.vm.provider :libvirt do |domain|
+          domain.uri = "qemu+ssh://user@remote1/system"
+        end
+      end
+      config.vm.define :test2 do |node|
+        node.vm.provider :libvirt do |domain|
+          domain.uri = "qemu+ssh://vms@remote2/system"
+        end
+      end
+    end
+    EOF
+  end
+  # need to override the default package iso_env as using a different
+  # name for the test machines above.
+  let(:machine)    { iso_env.machine(:test1, :libvirt) }
+  let(:machine2)   { iso_env.machine(:test2, :libvirt) }
+  let(:connection1) { double("connection 1") } 
+  let(:connection2) { double("connection 2") } 
+  let(:system_connection1) { double("system connection 1") } 
+  let(:system_connection2) { double("system connection 2") } 
+
+  describe '#connection' do
+    it 'should configure a separate connection per machine' do
+      expect(Fog::Compute).to receive(:new).with(
+        hash_including({:libvirt_uri => 'qemu+ssh://user@remote1/system'})).and_return(connection1)
+      expect(Fog::Compute).to receive(:new).with(
+        hash_including({:libvirt_uri => 'qemu+ssh://vms@remote2/system'})).and_return(connection2)
+
+      expect(machine.provider.driver.connection).to eq(connection1)
+      expect(machine2.provider.driver.connection).to eq(connection2)
+    end
+
+    it 'should configure the connection once' do
+      expect(Fog::Compute).to receive(:new).once().and_return(connection1)
+
+      expect(machine.provider.driver.connection).to eq(connection1)
+      expect(machine.provider.driver.connection).to eq(connection1)
+      expect(machine.provider.driver.connection).to eq(connection1)
+    end
+  end
+
+  describe '#system_connection' do
+    # note that the urls for the two tests are currently
+    # incorrect here as they should be the following:
+    #   qemu+ssh://user@remote1/system
+    #   qemu+ssh://vms@remote2/system
+    #
+    # In that the system uri should be resolved based on
+    # the provider uri so that for:
+    #   uri => qemu+ssh://user@remote1/session
+    # system_uri should be 'qemu+ssh://user@remote1/system'
+    # and not 'qemu:///system'.
+    it 'should configure a separate connection per machine' do
+      expect(Libvirt).to receive(:open).with('qemu:///system').and_return(system_connection1)
+      expect(Libvirt).to receive(:open).with('qemu:///system').and_return(system_connection2)
+
+      expect(machine.provider.driver.system_connection).to eq(system_connection1)
+      expect(machine2.provider.driver.system_connection).to eq(system_connection2)
+    end
+
+    it 'should configure the connection once' do
+      expect(Libvirt).to receive(:open).with('qemu:///system').and_return(system_connection1)
+
+      expect(machine.provider.driver.system_connection).to eq(system_connection1)
+      expect(machine.provider.driver.system_connection).to eq(system_connection1)
+      expect(machine.provider.driver.system_connection).to eq(system_connection1)
+    end
+  end
+end