Expand upon machine reachability to include port

[#166421517](https://www.pivotaltracker.com/story/show/166421517)
 Investigate customer issue with certificate validation in stembuild

Co-authored-by: Simon Jones <[email protected]>

Author: George Gelashvili

README.md

@@ -36,11 +36,11 @@ This command provisions and syspreps an existing VM on vCenter. It prepares a VM
 stembuild construct -vm-ip <IP of VM> -vm-username <vm username> -vm-password <vm password>  -vcenter-url <vCenter URL> -vcenter-username <vCenter username> -vcenter-password <vCenter password> -vm-inventory-path <vCenter VM inventory path>
 ```
 
-*Requirements*:
+### Requirements
 - LGPO.zip in current working directory
 - Running Windows VM with:
 	- Up to date Operating System
-	- Reachable by IP
+	- Reachable by IP over port 5985
 	- Username and password with Administrator privileges
 	- vCenter URL, username and password
 	- vCenter Inventory Path
@@ -70,6 +70,11 @@ Flags:
 	
 ```
 
+### Troubleshooting
+After running `stembuild construct`, you may find yourself with a connection issue to the VM
+- Confirm port 5985 is reachable via something like `nmap [vm-ip] -Pn`
+
+
 ## `stembuild package`
 
 This command creates a BOSH Stemcell from a provisioned vCenter VM