Map performance column name to metric column name

Currently the alert for Normal Operating Range never trigger because of two errors:
1. The mapping of operator has an error. It should resolve into either > or <
2. Column name to get historical average data from vim_performance_operting_ranges and column name to get real time data from metrics are different. The code assumed them the same.

https://bugzilla.redhat.com/show_bug.cgi?id=1142308
Style: Align the case with the whens.  One of

```ruby
x = case y
    when z
    end

# or

x =
  case y
  when z
  end
```

I prefer the latter, but that's just me.