exception: in ids mode, only REJECT the packet

In case of 'EXCEPTION_POLICY_REJECT', we were applying the same behavior
regardless of being in IDS or IPS mode.
This meant that at least the 'flow.action' was changed to drop when we
hit an exception policy in IDS mode. This minor fix makes the SV test
pass, but I'm afraid the bug can mean more than that.

Bug #6109

src/util-exception-policy.c

@@ -72,6 +72,9 @@ void ExceptionPolicyApply(Packet *p, enum ExceptionPolicy policy, enum PacketDro
         case EXCEPTION_POLICY_REJECT:
             SCLogDebug("EXCEPTION_POLICY_REJECT");
             PacketDrop(p, ACTION_REJECT, drop_reason);
+            if (!EngineModeIsIPS()) {
+                break;
+            }
             /* fall through */
         case EXCEPTION_POLICY_DROP_FLOW:
             SCLogDebug("EXCEPTION_POLICY_DROP_FLOW");