child-sa: Introduce a CHILD_RETRYING state to detect DH group retries

src/libcharon/sa/child_sa.c

@@ -34,6 +34,7 @@ ENUM(child_sa_state_names, CHILD_CREATED, CHILD_DESTROYING,
 	"INSTALLED",
 	"UPDATING",
 	"REKEYING",
+	"RETRYING",
 	"DELETING",
 	"DESTROYING",
 );