Suppress compiler warnings for older Emacsen in tramp-tests.el

* test/lisp/net/tramp-tests.el (tramp-test17-insert-directory):
Add error name to test.
(tramp-test30-make-process, tramp-test45-unload):
Suppress compiler warnings from older Emacsen.
2 jobs for master in 64 minutes and 4 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Test
passed #1814
test-all

01:04:04

passed #1815
test-filenotify-gio

00:45:50