Cluster: make sortGetKeys() able to handle multiple STORE options.

It does not make sense to pass multiple store options, so, better to
handle it ;-)

src/db.c

@@ -1064,7 +1064,10 @@ int *sortGetKeys(struct redisCommand *cmd, robj **argv, int argc, int *numkeys)
                 i += skiplist[j].skip;
                 break;
             } else if (!strcasecmp(argv[i]->ptr,"store") && i+1 < argc) {
-                keys[num++] = i+1; /* <store-key> */
+                /* Note: we don't increment "num" here and continue the loop
+                 * to be sure to process the *last* "STORE" option if multiple
+                 * ones are provided. This is same behavior as SORT. */
+                keys[num] = i+1; /* <store-key> */
                 break;
             }
         }