Make Tramp's async processes more robust

Make Tramp's async processes more robust

* lisp/simple.el (shell-command-sentinel): Check process property
`remote-command' first.

* lisp/net/tramp.el (tramp-handle-make-process):
* lisp/net/tramp-androidsu.el (tramp-androidsu-handle-make-process):
Set sentinel `ignore'.  (Bug#71049)

* test/lisp/net/tramp-tests.el
(tramp--test-deftest-direct-async-process): Don't suppress
internal sentinel.
(tramp-test32-shell-commanddirect-async): Don't tag it :unstable.

(cherry picked from commit 91509d5d2a2dc818830cff63f13d6efcb229dc0c)