YubiKey: Retry to recover hotplugging

* Attempt one retry in the event the event the device was removed and
  re-inserted.

Signed-off-by: Kyle Manna <kyle@kylemanna.com>

src/keys/YkChallengeResponseKey.h

@@ -31,7 +31,8 @@ public:
 
     QByteArray rawKey() const;
     YkChallengeResponseKey* clone() const;
-    bool challenge(const QByteArray& challenge);
+    bool challenge(const QByteArray& chal);
+    bool challenge(const QByteArray& chal, int retries);
     QString getName() const;
     bool isBlocking() const;