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
Following the footsteps of other clients like Firefox/Chrome. RFC 6761
says clients SHOULD do this.
Add test 389 to verify.
Reported-by: TheKnarf on github
Fixes#9192Closes#9296