[builtins/jsonrpc] Invert default for showing dialogs after 5324.

This is to ensure backward compatibility with skins/add-ons (type="action"),
add-ons directly calling built-in functions, third party applications using the
JSON-RPC API and existing key mappings.
Merge pull request #5625 from anaconda/fix-5324-remotes

[builtins] Invert default for showing dialogs after 5324 for remotes/add-ons.