BUG/MINOR: http-rules: Return ACT_RET_ABRT to abort a transaction

BUG/MINOR: http-rules: Return ACT_RET_ABRT to abort a transaction

When an action interrupts a transaction, returning a response or not, it must
return the ACT_RET_ABRT value and not ACT_RET_DONE. ACT_RET_DONE is reserved to
stop the processing on the current channel but some analysers may still be
active. When ACT_RET_ABRT is returned, all analysers are removed, except FLT_END
if it is set.

No backport needed because on previous verions, the action return value was not
handled the same way.

It is stated in the comment the return action returns ACT_RET_ABRT on
success. It it the right code to use to abort a transaction. ACT_RET_DONE must
be used when the message processing must be stopped. This does not means the
transaction is interrupted.

No backport needed.