[core] use Excon :persistent option

fog.gemspec

@@ -42,7 +42,7 @@ Gem::Specification.new do |s|
   ## List your runtime dependencies here. Runtime dependencies are those
   ## that are needed for an end user to actually USE your code.
   s.add_dependency('builder')
-  s.add_dependency('excon', '~>0.30.0')
+  s.add_dependency('excon', '~>0.31.0')
   s.add_dependency('formatador', '~>0.2.0')
   s.add_dependency('multi_json', '~>1.0')
   s.add_dependency('mime-types')

lib/fog/core/connection.rb

@@ -30,8 +30,8 @@ def initialize(url, persistent=false, params={})
         end
         params[:headers] ||= {}
         params[:headers]['User-Agent'] ||= "fog/#{Fog::VERSION}"
+        params.merge!(:persistent => params.fetch(:persistent, persistent))
         @excon = Excon.new(url, params)
-        @persistent = persistent
       end
 
       # Makes a request using the connection using Excon
@@ -53,7 +53,6 @@ def initialize(url, persistent=false, params={})
       # @raise [Excon::Errors::SocketError]
       #
       def request(params, &block)
-        reset unless @persistent
         @excon.request(params, &block)
       end