exceptions: add reject support to exception policy

exceptions: add reject support to exception policy

This enables the usage of 'reject' as an exception policy. As for both
IPS and IDS modes the intended result of sending a reject packet is to
reject the related flow, this will effectively mean setting the reject
action to the packet that triggered the exception condition, and then
dropping the associated flow.

Task #5503

(cherry picked from commit bbd968c738230b4f77de3278994c4fd5aa859dcd)