detect: reset signature groups when reversing flow

detect: reset signature groups when reversing flow

Ticket: 7552

When we use midstream, and the first packet we see of a flow is
a response from server, and we want to match on some signature
to client :
- we had first set sgh_toserver/FLOW_SGH_TOSERVER as we first
  thought this was a packet to server
- we then swap/reverse the flow, so sgh_toclient becomes sgh_toserver
  but it contains signatures to server and cannot match our
  to_client signature

The detect engine with DetectRunSetup will set again the
signatures group heads properly