BUG/MEDIUM: conn-stream: Don't erase endpoint flags on reset

Only CS_EP_ERROR flag is now removed from the endpoint when a reset is
performed. When a new the endpoint is allocated, flags are preserved. It is
the caller responsibility to remove other flags, depending on its need.

Concretly, during a connection retry or a L7 retry, we must preserve
flags. In tcpcheck and the CLI, we reset flags.

This patch is 2.6-specific. No backport needed.
diff --git a/src/cli.c b/src/cli.c
index 081d28c..b32b8b1 100644
--- a/src/cli.c
+++ b/src/cli.c
@@ -2761,6 +2761,7 @@
 					s->srv_error(s, s->csb);
 				return 1;
 			}
+			s->csb->endp->flags &= CS_EP_DETACHED;
 		}
 
 		sockaddr_free(&s->csb->dst);