provide flexibility in packer servers with more then one NIC,

when a packer server has more then one NIC, Packer can often
select the wrong http server using {{ .HTTPIP }}. We extend the
variables file to include an http_server_address which can be set
to the IP address of the correct NIC. This configuration propagates down
to the http_bind_address directive of the builder and the boot_command
entered on the guest VM. Adding 0.0.0.0 as a reasonable default as it
preserves comptability with packers default behavior.

This commit was required to get Packer to build the ubuntu guest
successfully in our environment

Additional Reading:
hashicorp/packer#9973
https://www.packer.io/docs/builders/vmware/vsphere-iso#http-directory-configuration

ESXi/Packer/ubuntu1804_esxi.json

@@ -21,7 +21,7 @@
                 " netcfg/get_domain=vm<wait>",
                 " netcfg/get_hostname=vagrant<wait>",
                 " grub-installer/bootdev=/dev/sda<wait>",
-                " preseed/url=http://{{ .HTTPIP }}:{{ .HTTPPort }}/preseed.cfg<wait>",
+                " preseed/url=http://{{user `http_server_address`}}:{{ .HTTPPort }}/preseed.cfg<wait>",
                 " -- <wait>",
                 "<enter><wait>"
             ],
@@ -30,6 +30,7 @@
             "disk_size": "{{user `disk_size`}}",
             "guest_os_type": "ubuntu-64",
             "http_directory": "{{user `http_directory`}}",
+            "http_bind_address": "{{user `http_server_address`}}",
             "iso_checksum": "{{user `iso_checksum`}}",
             "iso_url": "{{user `mirror`}}/{{user `mirror_directory`}}/{{user `iso_name`}}",
             "keep_registered": true,
@@ -90,6 +91,7 @@
     "variables": {
         "box_basename": "ubuntu-18.04",
         "http_directory": "{{template_dir}}/http",
+        "http_server_address": "",
         "build_timestamp": "{{isotime \"20060102150405\"}}",
         "cpus": "2",
         "disk_size": "65536",

ESXi/Packer/variables.json

@@ -3,5 +3,6 @@
     "esxi_datastore": "",
     "esxi_username": "",
     "esxi_password": "",
-    "esxi_network_with_dhcp_and_internet": ""
+    "esxi_network_with_dhcp_and_internet": "",
+    "http_server_address": "0.0.0.0"
 }