redis-benchmark: Remove unused buffer

This just deletes old code that didn't get removed when
logic changed.  We were setting offsets that never
got read anywhere.

Since clients are now just cloned, we don't need to track
per-client buffer offsets anywhere because they are all
the same from the original client.

src/redis-benchmark.c

@@ -398,15 +398,6 @@ static client createClient(char *cmd, size_t len, client from) {
 
 static void createMissingClients(client c) {
     int n = 0;
-    char *buf = c->obuf;
-    size_t buflen = sdslen(c->obuf);
-
-    /* If we are cloning from a client with a SELECT prefix, skip it since the
-     * client will be created with the prefixed SELECT if needed. */
-    if (c->selectlen) {
-        buf += c->selectlen;
-        buflen -= c->selectlen;
-    }
 
     while(config.liveclients < config.numclients) {
         createClient(NULL,0,c);