Start unbound with intended arguments

Unbound looked like it was meant to be started as if by `unbound -c /etc/unbound/unbound.conf`, but instead the string `-c /etc/unbound/unbound.conf` was set as argv[0] of the unbound command, meaning it is never parsed.

optional/unbound/start.py

@@ -10,4 +10,4 @@ system.set_env()
 
 conf.jinja("/unbound.conf", os.environ, "/etc/unbound/unbound.conf")
 
-os.execv("/usr/sbin/unbound", ["-c /etc/unbound/unbound.conf"])
+os.execv("/usr/sbin/unbound", ["unbound", "-c", "/etc/unbound/unbound.conf"])