conman:  Tweak FrenzyWPACtrl.attached.

A normal WPACtrl can attach to wpa_supplicant even when not connected
to a network.  FrenzyWPACtrl cannot emulate this perfectly, but
currently (by requiring that there is an SSID) its `attached` method
requires that wpa_supplicant is actually connected to a network.
Removing this requirement and only requiring that the Quantenna chip
is in client mode is closer to the real WPACtrl behavior.

Change-Id: Ic5366baad7b784be2576b6df987ed0614131797b
diff --git a/conman/interface.py b/conman/interface.py
index 3acdf24..7c10d7a 100755
--- a/conman/interface.py
+++ b/conman/interface.py
@@ -454,7 +454,7 @@
     self._update()
 
   def attached(self):
-    return self._client_mode and self._ssid
+    return self._client_mode
 
   def detach(self):
     raise wpactrl.error('Real WPACtrl always raises this when detaching.')