build: move e2e dependencies into e2e/go.mod

Several packages are only used while running the e2e suite. These
packages are less important to update, as the they can not influence the
final executable that is part of the Ceph-CSI container-image.

By moving these dependencies out of the main Ceph-CSI go.mod, it is
easier to identify if a reported CVE affects Ceph-CSI, or only the
testing (like most of the Kubernetes CVEs).

Signed-off-by: Niels de Vos <ndevos@ibm.com>

e2e/vendor/github.com/NYTimes/gziphandler/README.md

@@ -0,0 +1,56 @@
+Gzip Handler
+============
+
+This is a tiny Go package which wraps HTTP handlers to transparently gzip the
+response body, for clients which support it. Although it's usually simpler to
+leave that to a reverse proxy (like nginx or Varnish), this package is useful
+when that's undesirable.
+
+## Install
+```bash
+go get -u github.com/NYTimes/gziphandler
+```
+
+## Usage
+
+Call `GzipHandler` with any handler (an object which implements the
+`http.Handler` interface), and it'll return a new handler which gzips the
+response. For example:
+
+```go
+package main
+
+import (
+	"io"
+	"net/http"
+	"github.com/NYTimes/gziphandler"
+)
+
+func main() {
+	withoutGz := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "text/plain")
+		io.WriteString(w, "Hello, World")
+	})
+
+	withGz := gziphandler.GzipHandler(withoutGz)
+
+	http.Handle("/", withGz)
+	http.ListenAndServe("0.0.0.0:8000", nil)
+}
+```
+
+
+## Documentation
+
+The docs can be found at [godoc.org][docs], as usual.
+
+
+## License
+
+[Apache 2.0][license].
+
+
+
+
+[docs]:     https://godoc.org/github.com/NYTimes/gziphandler
+[license]:  https://github.com/NYTimes/gziphandler/blob/master/LICENSE