p2p: Ignore CMPCTBLOCK from peer that hasn't sent SENDCMPCT

This commit also changes the default sendcmpct version in the functional
test to `2`, since this is the version that nodes expect, prior to this
commit, nowhere in the functional test framework was the default version
value used:

git grep -P 'msg_sendcmpct\((?![^)]*version\s*=)' HEAD^

`version=2` is a sensible default, since this is the version nodes
currently expect in the SENDCMPCT handshake.

test/functional/test_framework/messages.py

@@ -1672,7 +1672,7 @@ class msg_sendcmpct:
     __slots__ = ("announce", "version")
     msgtype = b"sendcmpct"
 
-    def __init__(self, announce=False, version=1):
+    def __init__(self, announce=False, version=2):
         self.announce = announce
         self.version = version