message: fix miningtest error detection to reflect slightly different way incorrect id is being reported
diff: @@ -44,7 +44,8 @@ class MyTest (BitcoinTestFramework):
  del c["prevhash"]
  id = c["id"]
  c["id"] = 100000 # bad ID
  - expectException(lambda: node.submitminingsolution(c), JSONRPCException)
  + ret = node.submitminingsolution(c)
  + assert ret == "id not found"
  # didn't provide a nonce
  c = node.getminingcandidate()
  