PT-2340 - Support MySQL 8.4

- Added wait_for_replicas call into t/pt-table-checksum/pt-1616.t
- Added diagnostic output into t/pt-upgrade/run_time.t, t/pt-table-sync/issue_627.t

t/pt-table-checksum/pt-1616.t

@@ -105,5 +105,6 @@ unlike(
 # Done.
 # #############################################################################
 $sb->wipe_clean($dbh);
+$sb->wait_for_replicas();
 ok($sb->ok(), "Sandbox servers") or BAIL_OUT(__FILE__ . " broke the sandbox");
 exit;

t/pt-table-sync/issue_627.t

@@ -61,7 +61,7 @@ is(
 REPLACE INTO `issue_375`.`t`(`id`, `updated_at`, `foo`) VALUES ('100', '2009-09-06 15:01:23', 'cv');
 ",
    'Simple --replicate'
-);
+) or diag($output);
 
 # Note how the columns are out of order (tbl order is: id, updated_at, foo).
 # This is issue http://code.google.com/p/maatkit/issues/detail?id=371

t/pt-upgrade/run_time.t

@@ -60,7 +60,7 @@ my $t = time - $t0;
 
 ok(
    $t >= 3 && $t <= ($ENV{PERCONA_SLOW_BOX} ? 8 : 6),
-   "Exec queries: ran for roughly --run-time seconds"
+   "Exec queries: ran for roughly 3 seconds"
 ) or diag($output, 'Actual run time:', $t);
 
 # Exit status 8 = --run-time expired (an no other errors/problems)