[BUGFIX] FAL links in RTE not transformed when link has rel attribute

Problem: When the RTE inserts the link, the href looks like
http://somedomain/?file:1234. If a rel attribute is present, the link
is not transformed into a typolink on the way to the database.
However, the href attribute is not transformed, as it should, into a
normal file url. It should because the a-tag will be rendered as is in
the frontend.

Solution: When a link is not be transformed into a typolink,
transform the href into a normal file url.

Resolves: #54944
Release: 6.2
Change-Id: I92c45363ffd62de0f4e89941944f55320d4fc708
Reviewed-on: https://review.typo3.org/27142
Reviewed-by: Stefan Froemken
Tested-by: Stefan Froemken
Reviewed-by: Steffen Ritter
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters