Work on asynchronous processes for tramp-adb.el

Work on asynchronous processes for tramp-adb.el

* lisp/net/tramp-adb.el (tramp-adb-handle-make-process):
Simplify.  Remove echoed first line.
(tramp-adb-send-command): Add NEVEROPEN and NOOUTPUT.

* lisp/net/tramp-sh.el (tramp-process-sentinel): Remove.
(tramp-sh-handle-make-process): Simplify.

* lisp/net/tramp.el (tramp-process-sentinel): New defun, taken from
tramp-sh.el.  Delete trailing shell prompt.

* test/lisp/net/tramp-tests.el (tramp-test29-start-file-process)
(tramp-test30-make-process): Run also for tramp-adb.
(tramp-test32-shell-command): Remove tramp-adb restrictions.
(tramp-test34-explicit-shell-file-name): Rework.  Remove :unstable tag.