Use separate exceptions for open_timeout, timeout

Explicitly track which state we're in with a given connection so that
we know whether we've successfully established the TCP connection.

For timeouts occurring before we enter the body of the Net::HTTP#start
block, assume the request failed establishing the connection, and
raise the new RestClient::ConnectTimeout exception (which, for
compatibility, is a subclass of RestClient::RequestTimeout).

Unfortunately, this is a bit difficult to test without taking
advantage of actual network latency - it seems impossible to force
Linux to delay SYN/ACKing an incoming connection (even if you don't
accept() it and you have listen() backlog set to 0). However, testing
with a sufficiently low open_timeout and a sufficiently distant server
seems to work.

Conflicts:
    lib/restclient/request.rb

lib/restclient/exceptions.rb

@@ -193,6 +193,13 @@ def initialize(message)
       self.message = message
     end
   end
+
+  class ConnectTimeout < RequestTimeout
+    def initialize(message='Timed out connecting to server')
+      super nil, nil
+      self.message = message
+    end
+  end
 end
 
 class RestClient::Request

lib/restclient/request.rb

@@ -364,6 +364,8 @@ def print_verify_callback_warnings
     end
 
     def transmit uri, req, payload, & block
+      established_connection = false
+
       setup_credentials req
 
       net = net_http_class.new(uri.hostname, uri.port)
@@ -428,6 +430,8 @@ def transmit uri, req, payload, & block
 
 
       net.start do |http|
+        established_connection = true
+
         if @block_response
           net_http_do_request(http, req, payload ? payload.to_s : nil,
                               &@block_response)
@@ -441,8 +445,11 @@ def transmit uri, req, payload, & block
     rescue EOFError
       raise RestClient::ServerBrokeConnection
     rescue Timeout::Error, Errno::ETIMEDOUT
-      raise RestClient::RequestTimeout
-
+      if established_connection
+        raise RestClient::RequestTimeout
+      else
+        raise RestClient::ConnectTimeout
+      end
     rescue OpenSSL::SSL::SSLError => error
       # TODO: deprecate and remove RestClient::SSLCertificateNotVerified and just
       # pass through OpenSSL::SSL::SSLError directly.