[autotest] Add .conf to autotest-server apache site config file name.

Apache installed in Ubuntu 14 (trusty) does not recognize site config file
not ends with .conf.

BUG=None
TEST=tested in a trusty vm, test the script also works in Ubuntu 12.04
(chromeos-autotest.cbf)

Change-Id: I706c9c214ef3b5bd5b5912a901b6e6a37a7be8c4
Reviewed-on: https://chromium-review.googlesource.com/227611
Tested-by: Dan Shi <dshi@chromium.org>
Reviewed-by: Prashanth B <beeps@chromium.org>
Commit-Queue: Dan Shi <dshi@chromium.org>
diff --git a/site_utils/setup_dev_autotest.sh b/site_utils/setup_dev_autotest.sh
index f015746..ebf90a6 100755
--- a/site_utils/setup_dev_autotest.sh
+++ b/site_utils/setup_dev_autotest.sh
@@ -265,11 +265,11 @@
   sudo mkdir /etc/apache2/run
 fi
 sudo ln -sf "${AT_DIR}"/apache/apache-conf \
-  /etc/apache2/sites-available/autotest-server
+  /etc/apache2/sites-available/autotest-server.conf
 # disable currently active default
 sudo a2dissite default
 # enable autotest server
-sudo a2ensite autotest-server
+sudo a2ensite autotest-server.conf
 # Enable rewrite module
 sudo a2enmod rewrite
 # Enable wsgi