[TAP] Fix cancellation of a text formatting process.

Before this fix, cancelling a TAP job (async or not) which was formatting the
result in ASCII may failed, especially for large results. This was due to a
non interruptible alignment process. This process is now checking whether a
cancellation has been requested before formatting a new result line/row ; if so,
the process is immediately stopped and the job can be cleaning declared as
aborted.