[qa] Fixes segwit block relay test after inv-direct-fetch was disabled

This test was passing because we never fetch blocks if we only receive
an inv and not the header (after 037159cebf),
and this test wasn't delivering the header.

test/functional/p2p-segwit.py

@@ -61,16 +61,6 @@ class TestNode(NodeConnCB):
             self.send_message(msg)
         self.wait_for_getdata()
 
-    def announce_block(self, block, use_header):
-        with mininode_lock:
-            self.last_message.pop("getdata", None)
-        if use_header:
-            msg = msg_headers()
-            msg.headers = [ CBlockHeader(block) ]
-            self.send_message(msg)
-        else:
-            self.send_message(msg_inv(inv=[CInv(2, block.sha256)]))
-
     def request_block(self, blockhash, inv_type, timeout=60):
         with mininode_lock:
             self.last_message.pop("block", None)
@@ -1029,13 +1019,18 @@ class SegWitTest(BitcoinTestFramework):
             block4 = self.build_next_block(nVersion=4)
             block4.solve()
             self.old_node.getdataset = set()
+
             # Blocks can be requested via direct-fetch (immediately upon processing the announcement)
             # or via parallel download (with an indeterminate delay from processing the announcement)
             # so to test that a block is NOT requested, we could guess a time period to sleep for,
             # and then check. We can avoid the sleep() by taking advantage of transaction getdata's
             # being processed after block getdata's, and announce a transaction as well,
             # and then check to see if that particular getdata has been received.
-            self.old_node.announce_block(block4, use_header=False)
+            # Since 0.14, inv's will only be responded to with a getheaders, so send a header
+            # to announce this block.
+            msg = msg_headers()
+            msg.headers = [ CBlockHeader(block4) ]
+            self.old_node.send_message(msg)
             self.old_node.announce_tx_and_wait_for_getdata(block4.vtx[0])
             assert(block4.sha256 not in self.old_node.getdataset)