[test] wait for inital broadcast before comparing mempool entries

- mempool entry 'unbroadcast' field changes when tx passes initial broadcast (receive getdata),
so anytime you compare mempool entries as a whole, you must wait for all broadcasts to complete
('unbroadcast' = False) otherwise the state may change in between calls
- update P2PTxInvStore to send msg_getdata for invs and add functionality to wait for a list
of txids to complete initial broadcast
- make mempool_packages.py wait because it compares entries using getrawmempool and
getmempoolentry

test/functional/mempool_packages.py

@@ -7,6 +7,7 @@
 from decimal import Decimal
 
 from test_framework.messages import COIN
+from test_framework.mininode import P2PTxInvStore
 from test_framework.test_framework import BitcoinTestFramework
 from test_framework.util import (
     assert_equal,
@@ -58,6 +59,7 @@ class MempoolPackagesTest(BitcoinTestFramework):
 
     def run_test(self):
         # Mine some blocks and have them mature.
+        self.nodes[0].add_p2p_connection(P2PTxInvStore()) # keep track of invs
         self.nodes[0].generate(101)
         utxo = self.nodes[0].listunspent(10)
         txid = utxo[0]['txid']
@@ -72,6 +74,10 @@ class MempoolPackagesTest(BitcoinTestFramework):
             value = sent_value
             chain.append(txid)
 
+        # Wait until mempool transactions have passed initial broadcast (sent inv and received getdata)
+        # Otherwise, getrawmempool may be inconsistent with getmempoolentry if unbroadcast changes in between
+        self.nodes[0].p2p.wait_for_broadcast(chain)
+
         # Check mempool has MAX_ANCESTORS transactions in it, and descendant and ancestor
         # count and fees should look correct
         mempool = self.nodes[0].getrawmempool(True)