LogStash::Agent metrics after config reloading when reloading a config that raises exception on pipeline.run does not increase the successful reload count

```
Failures:

1) LogStash::Agent metrics after config reloading when reloading a config that raises exception on pipeline.run does not increase the successful reload count
Failure/Error: expect { subject.send(:"reload_pipeline!", "main") }.to_not change {
expected result not to have changed, but did change from 0 to 1
# ./logstash-core/spec/logstash/agent_spec.rb:575:in `(root)'
# ./vendor/bundle/jruby/1.9/gems/rspec-wait-0.0.9/lib/rspec/wait.rb:46:in `(root)'
# ./rakelib/test.rake:49:in `(root)'
# ./vendor/bundle/jruby/1.9/gems/rake-12.0.0/lib/rake/task.rb:250:in `execute'
# ./vendor/bundle/jruby/1.9/gems/rake-12.0.0/lib/rake/task.rb:250:in `execute'
# ./vendor/bundle/jruby/1.9/gems/rake-12.0.0/lib/rake/task.rb:194:in `invoke_with_call_chain'
# ./vendor/bundle/jruby/1.9/gems/rake-12.0.0/lib/rake/task.rb:187:in `invoke_with_call_chain'
# ./vendor/bundle/jruby/1.9/gems/rake-12.0.0/lib/rake/task.rb:180:in `invoke'
# ./vendor/bundle/jruby/1.9/gems/rake-12.0.0/lib/rake/application.rb:152:in `invoke_task'
# ./vendor/bundle/jruby/1.9/gems/rake-12.0.0/lib/rake/application.rb:108:in `top_level'
# ./vendor/bundle/jruby/1.9/gems/rake-12.0.0/lib/rake/application.rb:108:in `top_level'
# ./vendor/bundle/jruby/1.9/gems/rake-12.0.0/lib/rake/application.rb:117:in `run_with_threads'
# ./vendor/bundle/jruby/1.9/gems/rake-12.0.0/lib/rake/application.rb:102:in `top_level'
# ./vendor/bundle/jruby/1.9/gems/rake-12.0.0/lib/rake/application.rb:80:in `run'
# ./vendor/bundle/jruby/1.9/gems/rake-12.0.0/lib/rake/application.rb:178:in `standard_exception_handling'
# ./vendor/bundle/jruby/1.9/gems/rake-12.0.0/lib/rake/application.rb:77:in `run'
# ./vendor/bundle/jruby/1.9/gems/rake-12.0.0/exe/rake:27:in `(root)'
```