Bump mocktime before generating new blocks and generate a few blocks at the end of test_mempool_doublespend in p2p-instantsend.py (#3125)

* Cleanup p2p-instantsend.py

Bump mocktime before generating new blocks and generate a few blocks at the end of test_mempool_doublespend to clean things up

* Update test/functional/p2p-instantsend.py

Co-Authored-By: PastaPastaPasta <6443210+PastaPastaPasta@users.noreply.github.com>

Author: UdjinM6

test/functional/p2p-instantsend.py

@@ -9,7 +9,9 @@
     assert_raises_rpc_error
 
 '''
-InstantSendTest -- test InstantSend functionality (prevent doublespend for unconfirmed transactions)
+p2p-instantsend.py
+
+Tests InstantSend functionality (prevent doublespend for unconfirmed transactions)
 '''
 
 class InstantSendTest(DashTestFramework):
@@ -40,6 +42,8 @@ def test_block_doublespend(self):
         # feed the sender with some balance
         sender_addr = sender.getnewaddress()
         self.nodes[0].sendtoaddress(sender_addr, 1)
+        self.bump_mocktime(1)
+        set_node_times(self.nodes, self.mocktime)
         self.nodes[0].generate(2)
         self.sync_all()
 
@@ -92,6 +96,8 @@ def test_mempool_doublespend(self):
         # feed the sender with some balance
         sender_addr = sender.getnewaddress()
         self.nodes[0].sendtoaddress(sender_addr, 1)
+        self.bump_mocktime(1)
+        set_node_times(self.nodes, self.mocktime)
         self.nodes[0].generate(2)
         self.sync_all()
 
@@ -120,6 +126,11 @@ def test_mempool_doublespend(self):
         # send coins back to the controller node without waiting for confirmations
         receiver.sendtoaddress(self.nodes[0].getnewaddress(), 0.9, "", "", True)
         assert_equal(receiver.getwalletinfo()["balance"], 0)
+        # mine more blocks
+        self.bump_mocktime(1)
+        set_node_times(self.nodes, self.mocktime)
+        self.nodes[0].generate(2)
+        self.sync_all()
 
 if __name__ == '__main__':
     InstantSendTest().main()