Move RetryCountExceeded into common.rb

Author: aramprice

src/bosh_common/lib/common/common.rb

@@ -1,11 +1,12 @@
-require 'common/errors'
 require 'common/retryable'
 
 module Bosh
 
   # Module for common methods used throughout the BOSH code.
   module Common
 
+    class RetryCountExceeded < StandardError; end
+
     # Converts all keys of a [Hash] to symbols. Performs deep conversion.
     #
     # @param [Hash] hash to convert