some tests fail in 9.11 if newer bind.keys file is installed
System tests that don't specify
dnssec-validation yes or
bindkeys-file in their configurations will try to open the installed
bind.keys file, and in 9.11 they fail because
trust-anchors isn't recognized.
In other branches this doesn't cause test failures but it should be cleaned up anyway; there's no good reason for a test to access installed files.