pool challenge doesn't need cryptographic security

* Use PHP's regular php_rand() function instead of mt_rand() because we
don't need cryptographic security for the test, and mt_rand() will seed
for us if it's unseeded.

* Adds a cluster test that should retreive connections from the pool.

library.c

@@ -1813,11 +1813,7 @@ redis_sock_check_liveness(RedisSock *redis_sock)
     }
 
     gettimeofday(&tv, NULL);
-    if (!BG(mt_rand_is_seeded)) {
-        php_mt_srand(GENERATE_SEED());
-    }
-
-    uniqid_len = snprintf(uniqid, sizeof(uniqid), "phpredis_pool:%08lx%05lx:%08" PRIx32, (long)tv.tv_sec, (long)tv.tv_usec, php_mt_rand());
+    uniqid_len = snprintf(uniqid, sizeof(uniqid), "phpredis_pool:%08lx%05lx:%08lx", (long)tv.tv_sec, (long)tv.tv_usec, (long)php_rand());
     redis_cmd_init_sstr(&cmd, 1, "ECHO", sizeof("ECHO") - 1);
     redis_cmd_append_sstr(&cmd, uniqid, uniqid_len);
     smart_string_0(&cmd);

tests/RedisClusterTest.php

@@ -665,6 +665,21 @@ public function testSlotCache() {
         ini_set('redis.clusters.cache_slots', 0);
     }
 
+    /* Regression test for connection pool liveness checks */
+    public function testConnectionPool() {
+        $prev_value = ini_get('redis.pconnect.pooling_enabled');
+        ini_set('redis.pconnect.pooling_enabled', 1);
+
+        $pong = 0;
+        for ($i = 0; $i < 10; $i++) {
+            $obj_rc = new RedisCluster(NULL, self::$_arr_node_map, 30, 30, true);
+            $pong += $obj_rc->ping("key:$i");
+        }
+
+        $this->assertEquals($pong, $i);
+        ini_set('redis.pconnect.pooling_enabled', $prev_value);
+    }
+
     /**
      * @inheritdoc
      */