Backport fixes of running instrumentation with the NewRelic test harness

After porting the instrumentation to be merged inside the NewRelic rpm
it was possible to run already existing functional testing for HTTP
client instrumentation which uncovered some failed expectations.

This commit backports those fixes.

See newrelic/newrelic-ruby-agent#249

lib/newrelic_httprb/instrumentation.rb

@@ -18,8 +18,6 @@ def perform_with_newrelic_trace(request, options)
 
         response = nil
         ::NewRelic::Agent::CrossAppTracing.tl_trace_http_request(wrapped_request) do
-          # RUBY-1244 Disable further tracing in request to avoid double
-          # counting if connection wasn't started (which calls request again).
           response = perform_without_newrelic_trace(request, options)
           ::NewRelicHTTP::HTTPResponse.new(response)
         end

lib/newrelic_httprb/wrappers.rb

@@ -1,5 +1,20 @@
 module NewRelicHTTP
-  HTTPResponse = NewRelic::Agent::HTTPClients::HTTPClientResponse
+  class HTTPResponse
+    attr_reader :response
+
+    def initialize(response)
+      @response = response
+    end
+
+    def [](key)
+      _, value = response.headers.find { |k,_| key.downcase == k.downcase }
+      value unless value.nil?
+    end
+
+    def to_hash
+      response.headers
+    end
+  end
 
   class HTTPRequest
     attr_reader :request, :uri
@@ -13,12 +28,16 @@ def type
       "http.rb"
     end
 
-    def method
-      request.verb
+    def host
+      if hostname = self['host']
+        hostname.split(':').first
+      else
+        request.host
+      end
     end
 
-    def host
-      request.socket_host
+    def method
+      request.verb.upcase
     end
 
     def [](key)