fellow_log: Reduce LOGBLK_MEMPOOL_SIZE to 2 to reduce HoL blocking

src/fellow_log.c

@@ -413,7 +413,7 @@ assert_seq_macros(void)
 #define LBUF_DSKPOOL_SIZE					\
 	((((1<<13) - 16) - 2 * sizeof(struct buddy_reqs)) /	\
 	(2 * sizeof(struct i_reqalloc)))
-#define LOGBLK_MEMPOOL_SIZE 4
+#define LOGBLK_MEMPOOL_SIZE 2
 //lint -e{506, 527}
 static void __attribute__((constructor))
 assert_lbuf_dsk_resv(void)