[server] hold connection to the db in tx_actions We can be called without a cnxset (e.g. from repoapi).

[wsgi] If multipart cannot parse the POST content, let it pass. multipart can only parse html form data. It the content_type is, for example, "application/json", get_posted_data should not fail but just stop trying to read the content. Closes #4421845

[devtools] Fix JS tests' HTML code