Revert "When listing DBus services, also list activatable services."

This reverts commit ef0e3ac22e.

Sebastian thinks best to revert this:

It seems to me the reason I needed to look at activatable sockets
might actually be a networkd bug, and I was in error about patch 0001.
On my machines (without DHCP), networkd quits after configuring the
links. I thought this had to do with network activation, but that was
probably mistaken. This was obscured by my testing the change by doing
systemctl stop/start on networkd; now that I actually unplugged the
network cable, I noticed no DBus messages are triggered by this on
this machine. Your test case might have had a similar problem
(networkd quitting on idle). Might be related to [1].

On another machine (with DHCP) networkd remains active all the time,
and patch 0002 works there. You might want to revert 0001, though:
Suppose someone’s running no manager at all, so that polling would be
required. Because networkd is still listed as activable, we would
refrain from polling – by mistake, because networkd doesn’t seem to
actually go active if we listen on its bus, and it’s listed as
activable even when it’s not configured. Connectivity-related messages
will come in when stopping/starting the service, but not when
unplugging the cable.

Utility/DBus.hs

@@ -22,14 +22,8 @@ type ServiceName = String
 
 listServiceNames :: Client -> IO [ServiceName]
 listServiceNames client = do
-	active <- do
 	reply <- callDBus client "ListNames" []
-		return $ fromVariant =<< headMaybe (methodReturnBody reply)
-	activatable <- do
-		reply <- callDBus client "ListActivatableNames" []
-		return $ fromVariant =<< headMaybe (methodReturnBody reply)
-	let service_names = fromMaybe [] active ++ fromMaybe [] activatable
-	return service_names
+	return $ fromMaybe [] $ fromVariant =<< headMaybe (methodReturnBody reply)
 
 callDBus :: Client -> MemberName -> [Variant] -> IO MethodReturn
 callDBus client name params = call_ client $