Rename wallet_accounts.py test

This is a separate commit because changing the test at the same time as
renaming it breaks git (and github) rename detection.

Author: ryanofsky

test/functional/test_runner.py

@@ -67,7 +67,7 @@
     'feature_segwit.py',
     # vv Tests less than 2m vv
     'wallet_basic.py',
-    'wallet_accounts.py',
+    'wallet_labels.py',
     'p2p_segwit.py',
     'wallet_dump.py',
     'rpc_listtransactions.py',