[test] wait for disconnect_p2ps to be reflected in getpeerinfo

-Waiting is important to avoid race conditions,
especially if testing peer info through rpc later.
-Wait for mininodes to be disconnected only, even
though it's more complex, because we may still want
to be connected to test nodes.

test/functional/test_framework/test_node.py

@@ -23,6 +23,7 @@
 
 from .authproxy import JSONRPCException
 from .descriptors import descsum_create
+from .messages import MY_SUBVERSION
 from .util import (
     MAX_NODES,
     append_config,
@@ -549,11 +550,16 @@ def p2p(self):
         assert self.p2ps, self._node_msg("No p2p connection")
         return self.p2ps[0]
 
+    def num_connected_mininodes(self):
+        """Return number of test framework p2p connections to the node."""
+        return len([peer for peer in self.getpeerinfo() if peer['subver'] == MY_SUBVERSION])
+
     def disconnect_p2ps(self):
         """Close all p2p connections to the node."""
         for p in self.p2ps:
             p.peer_disconnect()
         del self.p2ps[:]
+        wait_until(lambda: self.num_connected_mininodes() == 0)
 
 
 class TestNodeCLIAttr: