Failure improvements

When I delete all jobs via button, I realized that jobs were dropped, 
but I have " a Failed count"  >  0 and no way to reset this counter.

I opened the console, and try to got this number via sidekiq-failures api 
```ruby
Sidekiq::RedisConnection.create.with{|a| a.zcard(:failed)}
2014-05-05T21:48:50Z 10350 TID-znnu9k INFO: Sidekiq client with redis options {}
=> 0
```
Then, I opened the sidekiq api, I got another way to get this number 
```ruby
 Sidekiq::Stats.new.failed
```
This is the right counter.

So I had replaced counter and move button from @failures.size condition, to reset counter anyway, there are Failed jobs or not.