tests: remove leading spaces from some tags

The threee tags `<name>`, `</name>` and `<command>` were frequently used
with a leading space that this removes. The reason this habbit is so

tests: remove leading spaces from some tags

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

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test{898,974,976}: add 'HTTP proxy' keywords

... so the tests can be automatically skipped when
testing external HTTP proxies like Privoxy.

Closes #8791

test 898/974/976: require proxy to run

Fixes #8755
Reported-by: Marc Hörsken
Closes #8756

test898: verify the fix for CVE-2022-27776

Do not pass on Authorization headers on redirects to another port