switch to wget results in no motd-news in clouds

cloud-specific motd news relies on the user-agent string cloud_id/<cloud-name> being included in the user-agent. The server, when receiving this string, will try to return the cloud-specific index file, which is `index.txt.<cloud-name>`. If that file doesn't exist, then the 404 error document is returned, which happens to be set to the default `index.txt` normal motd-news file.

curl happily returns that without flagging this as an error situation (a 404: it needs an extra command-line argument for that). wget, however, fails without printing the error document:

$ wget -U cloud_id/aws https://motd.ubuntu.com -O-
--2020-07-27 15:45:47-- https://motd.ubuntu.com/
Resolving motd.ubuntu.com (motd.ubuntu.com)... 54.171.230.55, 34.249.145.219, 2a05:d018:91c:3200:c887:2f22:290f:a7c, ...
Connecting to motd.ubuntu.com (motd.ubuntu.com)|54.171.230.55|:443... connected.
HTTP request sent, awaiting response... 404 Not Found
2020-07-27 15:45:48 ERROR 404: Not Found.

Not only that, it will also fail in its exit status:
$ echo $?
8

Whereas curl didn't:
$ curl -A cloud_id/aws https://motd.ubuntu.com
 * "If you've been waiting for the perfect Kubernetes dev solution for
   macOS, the wait is over. Learn how to install Microk8s on macOS."

   https://www.techrepublic.com/article/how-to-install-microk8s-on-macos/
$ echo $?
0
$

We need to pass --content-on-error, ignore the error status 8 (or all?) and make it quiet (-q):

$ wget -U cloud_id/aws https://motd.ubuntu.com -O- --content-on-error -q ; echo $?
 * "If you've been waiting for the perfect Kubernetes dev solution for
   macOS, the wait is over. Learn how to install Microk8s on macOS."

   https://www.techrepublic.com/article/how-to-install-microk8s-on-macos/
8