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
which caused an error when the second header was dumped due to stdout
being closed. Added test case 1066 to verify. Also fixed a potential
problem where a closed file descriptor might be used for an upload
when more than one URL is given.