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
When checking for a connection to re-use, a proxy-using request must
check for and use a proxy connection and not one based on the host
name!
Added test 1421 to verify
Bug: http://curl.haxx.se/bug/view.cgi?id=1492
