Don’t give up workflow when task returns false anymore

[linkyndy]

This reverts an earlier change. Workflows are not given up anymore if a task would return false. This was not intuitive and could potentially hide an actual issue within the task. Given up workflows would also be persisted for quite some time, which shouldn't happen, given there was no error or failed task. In the end, this broke Pallets' contract of defining a workflows contract from the beginning and being able to follow execution through all of its tasks; short-circuiting would mean workflows could complete without executing all tasks. A similar behaviour can be achieved by setting a context key and adding check it on the subsequent task(s).