Only actually needed servers should be listed and none is then implied
if no servers are listed.
Outputs a warning if "none" is still set as a server.
Closes#18466
The threee tags `<name>`, `</name>` and `<command>` were frequently used
with a leading space that this removes. The reason this habbit is so
widespread in testcases is probably that they have been copy and pasted.
Hence, fixing them all now might curb this practice from now on.
Closes#12028
