starter: Use correct type for uniqueids field

Enum arguments (ARG_ENUM with .list != LST_bool) are assumed to be of
type/size int in assign_args() in args.c.

Fixes: 0644ebd3de ("implemented IKE_SA uniqueness using ipsec.conf uniqueids paramater additionally supports a "keep" value to keep the old IKE_SA")

Closes strongswan/strongswan#2148

src/starter/confread.h

@@ -197,7 +197,7 @@ typedef struct starter_config starter_config_t;
 struct starter_config {
 		struct {
 				char     *charondebug;
-				bool     uniqueids;
+				int      uniqueids;
 				bool     cachecrls;
 				strict_t strictcrlpolicy;
 		} setup;