Add ability to get number of tokens.

Add a method to fetch the current number of available tokens.

userspace/engine/token_bucket.cpp

@@ -73,3 +73,8 @@ bool token_bucket::claim(uint64_t now)
 
 	return true;
 }
+
+double token_bucket::get_tokens()
+{
+	return m_tokens;
+}

userspace/engine/token_bucket.h

@@ -38,6 +38,10 @@ public:
 	// internal metrics.
 	//
 	bool claim(uint64_t now = 0);
+
+	// Return the current number of tokens available
+	double get_tokens();
+
 private:
 
 	//