Address memory leak on error

*** CID 1440371:  Resource leaks  (RESOURCE_LEAK)
/lib/isc/pool.c: 145 in isc_pool_expand()
139     
140     		/* Populate the new entries */
141     		for (i = pool->count; i < count; i++) {
142     			result = pool->init(&newpool->pool[i], pool->initarg);
143     			if (result != ISC_R_SUCCESS) {
144     				isc_pool_destroy(&pool);
   CID 1440371:  Resource leaks  (RESOURCE_LEAK)
   Variable "newpool" going out of scope leaks the storage it points to.
145     				return (result);
146     			}
147     		}
148     
149     		isc_pool_destroy(&pool);
150     		pool = newpool;