Improve robustness for out-of-band copy in Tramp

Improve robustness for out-of-band copy in Tramp

* lisp/net/tramp-adb.el (tramp-adb-execute-adb-command)
* lisp/net/tramp-cmds.el (tramp-append-tramp-buffers)
* lisp/net/tramp-gvfs.el (tramp-gvfs-do-copy-or-rename-file):
Cosmetic changes.

* lisp/net/tramp-sh.el (tramp-do-copy-or-rename-file-out-of-band):
Use local `default-directory'.  Simplify command to send.
Don't check return code, this was already done in
`tramp-process-actions'.
(tramp-get-inline-coding): Don't set `default-directory'.

* lisp/net/tramp.el (tramp-action-out-of-band):
Throw `out-of-band-failed'.
(tramp-process-actions): Handle `out-of-band-failed'.
(tramp-call-process, tramp-call-process-region):
Use local `default-directory'.