Copied net/http/serve_test.go as server_test.go

With modifications so it compiles. It does not pass yet

Signed-off-by: Abhijit Hiremagalur <abhi@pivotallabs.com>
Run proxy/server_test.go against built-in net/http

Most tests pass, compiles correctly against net/http

[#62920758]

Signed-off-by: Abhijit Hiremagalur <abhi@pivotallabs.com>
Move server_test.go alongside server/server.go

Signed-off-by: Abhijit Hiremagalur <abhi@pivotallabs.com>
Copy library net/http/httptest/server.go and switch it to our server/server.go

[#62920758]

Signed-off-by: Eric Malm <emalm@pivotallabs.com>