renewAll: error out if CERT_HOME is not a directory

With a misconfigured $HOME / CERT_HOME the glob over "$CERT_HOME"/*.*
matches nothing, so renewAll silently does nothing and returns success --
--renew-all / --cron appears to work while renewing no certificates.
Check that CERT_HOME is a directory up front and return 1 with a clear
error instead.

Closes #4508

acme.sh

@@ -6072,6 +6072,10 @@ renewAll() {
   _set_level=${NOTIFY_LEVEL:-$NOTIFY_LEVEL_DEFAULT}
   _debug "_set_level" "$_set_level"
   export _ACME_IN_RENEWALL=1
+  if ! [ -d "$CERT_HOME" ]; then
+    _err "$CERT_HOME is not a directory, please check your configuration."
+    return 1
+  fi
   for di in "${CERT_HOME}"/*.* "${CERT_HOME}"/*:*; do
     _debug di "$di"
     if ! [ -d "$di" ]; then