Add -ac option to allow remote connection to Xvfb

conf.d/xvfb.conf

@@ -1,3 +1,3 @@
 [program:xvfb]
-command=Xvfb :0 -screen 0 "%(ENV_DISPLAY_WIDTH)s"x"%(ENV_DISPLAY_HEIGHT)s"x24 -listen tcp
+command=Xvfb :0 -screen 0 "%(ENV_DISPLAY_WIDTH)s"x"%(ENV_DISPLAY_HEIGHT)s"x24 -listen tcp -ac
 autorestart=true