[MEDIUM] Fix stick-table replication on soft-restart

"[MINOR] session: add a pointer to the new target into the session" (664beb8)
introduced a regression by changing the type of a peer's target from
TARG_TYPE_PROXY to TARG_TYPE_NONE. The effect of this is that during
a soft-restart the new process no longer tries to connect to the
old process to replicate its stick tables.

This patch sets the type of a peer's target as TARG_TYPE_PROXY and
replication on soft-restart works once again.
diff --git a/src/peers.c b/src/peers.c
index 46a9178..26a3154 100644
--- a/src/peers.c
+++ b/src/peers.c
@@ -1184,7 +1184,7 @@
 	s->si[1].release = NULL;
 
 	session_init_srv_conn(s);
-	clear_target(&s->target);
+	set_target_proxy(&s->target, s->be);
 	s->pend_pos = NULL;
 
 	/* init store persistence */