Fix expected signature from Connman Scan method

Resulted in errors on app startup:
 Unexpected reply signature: got \"\", expected \"a{sv}\"

Connman technology interface documents Scan as void, results
gotten with other api.

Change-Id: I6f2961685af7e1ef0559e1b6d89245231404899c
Reviewed-by: Lorn Potter <lorn.potter@gmail.com>

src/plugins/bearer/connman/qconnmanservice_linux.cpp

@@ -506,7 +506,7 @@ void QConnmanTechnologyInterface::scan()
 
 void QConnmanTechnologyInterface::scanReply(QDBusPendingCallWatcher *call)
 {
-    QDBusPendingReply<QVariantMap> props_reply = *call;
+    QDBusPendingReply<void> props_reply = *call;
     if (props_reply.isError()) {
         qDebug() << props_reply.error().message();
     }