Adding missing hyphen to sudo options

builder/amazon/instance/builder.go

@@ -80,7 +80,7 @@ func (b *Builder) Prepare(raws ...interface{}) ([]string, error) {
 	}
 
 	if b.config.BundleVolCommand == "" {
-		b.config.BundleVolCommand = "sudo i -n ec2-bundle-vol " +
+		b.config.BundleVolCommand = "sudo -i -n ec2-bundle-vol " +
 			"-k {{.KeyPath}} " +
 			"-u {{.AccountId}} " +
 			"-c {{.CertPath}} " +

website/source/docs/builders/amazon-instance.html.markdown

@@ -270,7 +270,7 @@ is responsible for executing `ec2-bundle-vol` in order to store and image
 of the root filesystem to use to create the AMI.
 
 ```text
-sudo i -n ec2-bundle-vol \
+sudo -i -n ec2-bundle-vol \
 	-k {{.KeyPath}}  \
 	-u {{.AccountId}} \
 	-c {{.CertPath}} \
@@ -297,7 +297,7 @@ across multiple lines for convenience of reading. The bundle upload command
 is responsible for taking the bundled volume and uploading it to S3.
 
 ```text
-sudo i -n ec2-upload-bundle \
+sudo -i -n ec2-upload-bundle \
 	-b {{.BucketName}} \
 	-m {{.ManifestPath}} \
 	-a {{.AccessKey}} \