functional_tests: reset blockchain on test start

tests/functional_tests/cold_signing.py

@@ -38,10 +38,17 @@ from framework.wallet import Wallet
 
 class ColdSigningTest():
     def run_test(self):
+        self.reset()
         self.create(0)
         self.mine()
         self.transfer()
 
+    def reset(self):
+        print 'Resetting blockchain'
+        daemon = Daemon()
+        daemon.pop_blocks(1000)
+        daemon.flush_txpool()
+
     def create(self, idx):
         print 'Creating hot and cold wallet'