Suppress timers in Tramp operations

Suppress timers in Tramp operations

* lisp/net/tramp.el (tramp-accept-process-output):
* lisp/net/tramp-adb.el (tramp-adb-handle-start-file-process):
* lisp/net/tramp-sh.el (tramp-do-copy-or-rename-file-out-of-band)
(tramp-sh-handle-start-file-process):
* lisp/net/tramp-smb.el (tramp-smb-handle-copy-directory)
(tramp-smb-handle-file-acl, tramp-smb-handle-process-file)
(tramp-smb-handle-set-file-acl)
(tramp-smb-handle-start-file-process): Suppress timers.

* test/lisp/net/tramp-tests.el (tramp-test41-asynchronous-requests):
Use $REMOTE_PARALLEL_PROCESSES.  Flush cache prior file operations.
Add instrumentation messages.