[tests] Test disconnecting unsupported service bits logic.

In v0.15, we disconnect nodes that send us version messages with
unsupported service bits (1 << 5 and 1 << 7). This commit adds a test
that bitcoind will disconnect those nodes before August 1st 2018, and won't
disconnect those nodes after August 1st 2018.

test/functional/test_framework/mininode.py

@@ -51,6 +51,8 @@ NODE_NETWORK = (1 << 0)
 NODE_GETUTXO = (1 << 1)
 NODE_BLOOM = (1 << 2)
 NODE_WITNESS = (1 << 3)
+NODE_UNSUPPORTED_SERVICE_BIT_5 = (1 << 5)
+NODE_UNSUPPORTED_SERVICE_BIT_7 = (1 << 7)
 
 logger = logging.getLogger("TestFramework.mininode")