VMware: Fix usage of an alternate ESX/vCenter port

IPv6 addresses use square brackets to delimit address vs. port.
A comment in vim.py file incorrectly states the host and port can be
specified as host:port.  According to nova.conf, port isn't
even part of the host option.

This patch will create a separate port option to nova.conf instead
of allowing the port to be part of the host_ip option.

DocImpact: new host_port option added to nova.conf
Change-Id: Iebd415b5b3a9d2be42861220366135d2cb57b14d
Closes-bug: #1287292
Merge "VMware: Fix usage of an alternate ESX/vCenter port"