remote: Improve error message when libvirtd isn't running

While this could lead people in the wrong direction, people most commonly
hit this error when libvirtd isn't running, so let's mention a possible
fix.

src/remote/remote_driver.c

@@ -724,8 +724,8 @@ doRemoteOpen (virConnectPtr conn,
                 }
             }
             virReportSystemError(errno,
-                                 _("unable to connect to '%s'"),
-                                 sockname);
+              _("unable to connect to '%s', libvirtd may need to be started"),
+              sockname);
             goto failed;
         }