Fix subprocess creation in directories managed by tramp-androidsu

Fix subprocess creation in directories managed by tramp-androidsu

* lisp/net/tramp-androidsu.el
(tramp-androidsu-maybe-open-connection): Set connection property
remote-namespace to t or nil subject to whether su runs in the
global mount namespace.
(tramp-androidsu-adb-handle-make-process): Delete function.
(tramp-androidsu-make-process): New function.
(tramp-androidsu-file-name-handler-alist): Switch to
tramp-androidsu-make-process.

(cherry picked from commit 15ed441fd53ddb476a2a21c8717697a74cf094e1)