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/sirupsen/logrus/buffer_pool.go

@@ -0,0 +1,43 @@
+package logrus
+
+import (
+	"bytes"
+	"sync"
+)
+
+var (
+	bufferPool BufferPool
+)
+
+type BufferPool interface {
+	Put(*bytes.Buffer)
+	Get() *bytes.Buffer
+}
+
+type defaultPool struct {
+	pool *sync.Pool
+}
+
+func (p *defaultPool) Put(buf *bytes.Buffer) {
+	p.pool.Put(buf)
+}
+
+func (p *defaultPool) Get() *bytes.Buffer {
+	return p.pool.Get().(*bytes.Buffer)
+}
+
+// SetBufferPool allows to replace the default logrus buffer pool
+// to better meets the specific needs of an application.
+func SetBufferPool(bp BufferPool) {
+	bufferPool = bp
+}
+
+func init() {
+	SetBufferPool(&defaultPool{
+		pool: &sync.Pool{
+			New: func() interface{} {
+				return new(bytes.Buffer)
+			},
+		},
+	})
+}