Really mkdir /usr/local/etc in CI tests.

.github/run_test.sh

@@ -9,7 +9,7 @@ set -ex
 # If we want to test hostbased auth, set up the host for it.
 if [ ! -z "$SUDO" ] && [ ! -z "$TEST_SSH_HOSTBASED_AUTH" ]; then
     sshconf=/usr/local/etc
-    mkdir -p "${sshconf}"
+    $SUDO mkdir -p "${sshconf}"
     hostname | $SUDO tee $sshconf/shosts.equiv >/dev/null
     echo "EnableSSHKeysign yes" | $SUDO tee $sshconf/ssh_config >/dev/null
     $SUDO mkdir -p $sshconf