tests/frontend/run: Make waiting for the server less noisy

(imported from commit c62bc23081e76e18de2aeddf45a2e7043deabc2b)

zephyr/tests/frontend/run

@@ -33,9 +33,12 @@ ret = 1
 
 try:
     # Wait for the server to start up.
+    sys.stdout.write('Waiting for test server')
     while not server_is_up():
-        print 'Waiting for test server'
+        sys.stdout.write('.')
+        sys.stdout.flush()
         time.sleep(0.1)
+    sys.stdout.write('\n')
 
     ret = subprocess.call(
         'zephyr/tests/frontend/casperjs/bin/casperjs zephyr/tests/frontend/tests.js',