MINOR: peers: store the pointer to the signal handler

We'll need it to unregister stopped peers sections.
(cherry picked from commit aa729784e1c0a6a9ac003210d01c605962110522)
diff --git a/include/types/peers.h b/include/types/peers.h
index d52dc8c..b2d4566 100644
--- a/include/types/peers.h
+++ b/include/types/peers.h
@@ -56,6 +56,7 @@
 struct shared_table {
 	struct stktable *table;		    /* stick table to sync */
 	struct task *sync_task;		    /* main sync task */
+	struct sig_handler *sighandler;     /* signal handler */
 	struct peer_session *local_session; /* local peer session */
 	struct peer_session *sessions;	    /* peer sessions list */
 	unsigned int flags;		    /* current table resync state */