Make TX abort after assign safer

It is not right, but there are few examples when TX is aborted
after being assigned in case of error. To handle it better on
production systems add extra cleanup steps.

While here, replace couple dmu_tx_abort() in simple cases.

Reviewed-by: Rob Norris <robn@despairlabs.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Igor Kozhukhov <igor@dilos.org>
Signed-off-by: Alexander Motin <mav@FreeBSD.org>
Sponsored by: iXsystems, Inc.
Closes #17438