Fix error in Tramp loading, uncovered by tramp-test43-*

Fix error in Tramp loading, uncovered by tramp-test43-*

* lisp/net/tramp-archive.el (tramp-archive-autoload-file-name-handler):
New defalias.
(tramp-register-archive-file-name-handler): Use it.

* lisp/net/tramp.el (tramp-file-name-for-operation): Change it for
`expand-file-name'.
(tramp-file-name-handler): Unset `file-name-handler-alist' when
autoloading a Tramp file name handler.
(tramp-autoload-file-name-handler): Always unload Tramp file name
handlers.
(tramp-register-file-name-handlers)
(tramp-unload-file-name-handlers): Simplify.