BUG/MINOR: http-htx: Don't consider an URI as normalized after a set-uri action

BUG/MINOR: http-htx: Don't consider an URI as normalized after a set-uri action

An abosulte URI is marked as normalized if it comes from an H2 client. This
way, we know we can send a relative URI to an H1 server. But, after a
set-uri action, the URI must no longer be considered as normalized.
Otherwise there is no way to send an absolute URI on the server side.

If it is important to update a normalized absolute URI without altering this
property, the host, path and/or query-string must be set separatly.

This patch should fix the issue #1938. It should be backported as far as
2.4.