Duplicate typedef for metrics_store_t calls travis failure

src/lib/metrics/metrics_store.c:34:3: error: redefinition of typedef 'metrics_store_t' is a C11 feature [-Werror,-Wtypedef-redefinition] } metrics_store_t;

^ ./src/lib/metrics/metrics_store.h:19:32: note: previous definition is here typedef struct metrics_store_t metrics_store_t;

                           ^