Move is_interrupt_request check at the end of trigger_data_flush

The check was introduced by 3fc63536 to
fix a possible deadlock.

This however caused the trigger to not properly handle current
block_num, which was skipped because of early return. The block was not
pushed to the database and this later lead to foreign key violation when
updating `irreversible_data` table.

To fix the issue, move the check at the end of the trigger function,
after the current block is handled.