Add ability to configure networks for openstack

Add configuration option `networks`, a list of network UUIDs, to attach to the
source instance.

In some openstack installs, no default network will be attached or the network
with the ability to attach a public floating IP will need to be specified.

builder/openstack/builder.go

@@ -92,6 +92,7 @@ func (b *Builder) Run(ui packer.Ui, hook packer.Hook, cache packer.Cache) (packe
 			Flavor:         b.config.Flavor,
 			SourceImage:    b.config.SourceImage,
 			SecurityGroups: b.config.SecurityGroups,
+			Networks:       b.config.Networks,
 		},
 		&StepAllocateIp{
 			FloatingIpPool: b.config.FloatingIpPool,

builder/openstack/run_config.go

@@ -20,6 +20,7 @@ type RunConfig struct {
 	FloatingIpPool    string   `mapstructure:"floating_ip_pool"`
 	FloatingIp        string   `mapstructure:"floating_ip"`
 	SecurityGroups    []string `mapstructure:"security_groups"`
+	Networks          []string `mapstructure:"networks"`
 
 	// Unexported fields that are calculated from others
 	sshTimeout time.Duration

builder/openstack/step_run_source_server.go

@@ -13,6 +13,7 @@ type StepRunSourceServer struct {
 	Name           string
 	SourceImage    string
 	SecurityGroups []string
+	Networks       []string
 
 	server *gophercloud.Server
 }
@@ -30,12 +31,18 @@ func (s *StepRunSourceServer) Run(state multistep.StateBag) multistep.StepAction
 		securityGroups[i]["name"] = groupName
 	}
 
+	networks := make([]gophercloud.NetworkConfig, len(s.Networks))
+	for i, networkUuid := range s.Networks {
+		networks[i].Uuid = networkUuid
+	}
+
 	server := gophercloud.NewServer{
 		Name:          s.Name,
 		ImageRef:      s.SourceImage,
 		FlavorRef:     s.Flavor,
 		KeyPairName:   keyName,
 		SecurityGroup: securityGroups,
+		Networks:      networks,
 	}
 
 	serverResp, err := csp.CreateServer(server)

website/source/docs/builders/openstack.html.markdown

@@ -89,6 +89,8 @@ each category, the available configuration keys are alphabetized.
 <!---
 @todo document me
 -->
+* `networks` (array of strings) - A list of networks by UUID to attach
+  to this instance.
 
 * `security_groups` (array of strings) - A list of security groups by name
   to add to this instance.