Fixes "Host IP for the HyperV machine: False" if more than one VMNetworkAdapter is found

[BobSilent]

When using a Network Switch from docker (nat) where already container are attached to the network the call to Get-VMNetworkAdapter -ManagementOS -SwitchName "nat"

results in more than one adapter found, e.g.

Name                                 IsManagementOs VMName SwitchName MacAddress   Status IPAddresses
----                                 -------------- ------ ---------- ----------   ------ -----------
Container NIC 7ddd4f35               True                  nat        00155DAE7F3D {Ok}
F010C062-134C-4B70-A306-DA49FB6F64B8 True                  nat        00155DAE7720 {Ok}

In order to handle the situation, the powershell code was improved to handle more than one result (lists)

my assumption is, this one fixes
Closes #5023

although #4947 is marked as duplicate, it shows a different error information
==> hyperv-iso: Error getting host adapter ip address: PowerShell error: Get-VMNetworkAdapter : No network adapter is found with the given input.
therefore I am not sure if this also would fix #4947

[hashicorp-cla]

All committers have signed the CLA.

[BobSilent]

@SwampDragons can you support me? Is the travis build issue from my change? where do i have to look for details.

[SwampDragons]

Not you; we've been having some issues with Travis lately. I'll give this a quick test and then merge; it looks great!

[SwampDragons]

I'm having some trouble with my windows VM; it'll probably be a day or two before I can get to testing this. Sorry for the delay!

[BobSilent]

yeah, its always the infrastructure which makes trouble 😃
i was fighting the last days with my linux vms ;)

I am currently running my compiled version for this.
For testing i used the docker switch on my windows machine "nat" and just started a container (in my case a windows server core) which attached to the network, this gave me a simple way to have two managed network cards.

Another question, maybe a wrong place here, but i have some inputs for your description here https://github.com/hashicorp/packer/blob/master/.github/CONTRIBUTING.md#setting-up-go

As it was my first contact with GO and building on a windows machine.
When I followed the description (i manually downloaded make - http://gnuwin32.sourceforge.net/packages/make.htm)
I ran into this error:

C:\Projects\packer>make
...
# runtime/cgo
exec: "gcc": executable file not found in %PATH%

running this command,
go build -o bin/packer**.exe** .

I had to take care for a correct file ending in windows
and i am currently not sure if it really worked, because at the end
I installed mingw on windows

choco install mingw -y
Chocolatey v0.10.11
Installing the following packages:
mingw
By installing you accept licenses for the packages.
Progress: Downloading mingw 8.1.0... 100%

mingw v8.1.0 [Approved]

which made it possible to compile using make on windows without errors 🥇

[SwampDragons]

Do you think you could make a PR to the contributing.md with your suggestions? Those sound really valuable.

[ghost]

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