Fix Bug#24394, Bug#34172

Fix Bug#24394, Bug#34172

* lisp/subr.el (process-file-shell-command):
Use `with-connection-local-variables'.  Do not set "/bin/sh" for
remote buffers, trust settings of `shell-file-name'.

* lisp/net/tramp-adb.el (tramp-methods) <adb>:
* lisp/net/tramp-smb.el (tramp-methods) <smb>:
Remove `tramp-remote-shell' and `tramp-remote-shell-args'.

* lisp/net/tramp-sh.el (tramp-sh-handle-file-notify-add-watch)
(tramp-maybe-open-connection): Use proper read syntax for function
names.

* lisp/net/tramp.el (tramp-handle-shell-command): Do not use shell
file names from `tramp-methods'.
Respect `async-shell-command-buffer'.  (Bug#24394, Bug#34172)
Use `start-file-process-shell-command' and `process-file-shell-command'.

* test/lisp/net/tramp-tests.el (tramp-test32-shell-command):
Let it run partly for tramp-adb.