fn: URL parsing updates to fix json request_url (#657)

*) Updated fn-test-utils to latest fdk-go
*) Added hot-json to runner tests
*) Removed anon function in FromRequest which had
a side effect to set req.URL.Host. This is now more
explicit and eliminates some corresponding logic in
protocol http.
*) in gin, http request RequestURI is not set, removed
code that references this. (use Call.URL instead)

images/fn-test-utils/Gopkg.lock

@@ -5,7 +5,7 @@
   branch = "master"
   name = "github.com/fnproject/fdk-go"
   packages = ["."]
-  revision = "ce12b15e559bb56980c4134cbeadb99db9cd563a"
+  revision = "2d62538bfa636d3135c957ec7b78f2bedeeffa3d"
 
 [solve-meta]
   analyzer-name = "dep"