Fixing retry

Fixing the retry_policy. Previously, it wouldn't load as the require statement had a leading slash. It also tried calling should_retry? which was defined as should_try? so that wouldn't work. Also, any HTTP response other than 200 would raise an exception that would prevent the retry_policy from operating. So I added a rescue that saves the exception so it can be used/evaluated by retry logic.

To use, do something like:

    require "azure"
    require "azure/core/http/debug_filter"
    require "azure/core/http/retry_policy"
    retry_thing = Azure::Core::Http::RetryPolicy.new { |response, data| 
      return false unless data.has_key?(:error)
      if data.has_key?(:count) then
        data[:count] += 1
        return false if data[:count] > 3
      else
        data[:count] = 0
      end
      puts "current count #{data[:count]}"
      return true
    }

This checks to see if an error was captured, and if so initializes a retry count, then increments each retry attempt, finally returning false when count > 3.