erp5_api_style: abort transaction on error

When an error was encountered in `jIOWebSection`, it did not abort the
transaction, as it usually does in ERP5. This was made on purpose because
errors are logged in ZODB, hence aborting the transaction didn't make it
possible.

This behavior was annoying, so this commit purposedly abort transaction before
starting a new one to handle error. We are therefore able to log error in ZODB
while also keeping the usual ERP5 behavior of aborting on error.