test: Don't return the result of checking for running emacs to the tester.

When checking for a running emacs, test_emacs evaluates the empty list
'()'. This returns 'nil' when emacs is running, which is then
prepended to the actual test result. Given that it is not part of the
actual test output the test harness can incorrectly report test
failure (or success).

test/test-lib.sh

@@ -926,7 +926,7 @@ test_emacs () {
 				--eval '(orphan-watchdog $$)'" || return
 		EMACS_SERVER="$server_name"
 		# wait until the emacs server is up
-		until test_emacs '()' 2>/dev/null; do
+		until test_emacs '()' >/dev/null 2>/dev/null; do
 			sleep 1
 		done
 	fi