enhance and fix log calls

Some of these changes are cosmetic (repeatedly calling klog.V instead of
reusing the result), others address real issues:

- Logging a message only above a certain verbosity threshold without
  recording that verbosity level (if klog.V().Enabled() { klog.Info... }):
  this matters when using a logging backend which records the verbosity
  level.

- Passing a format string with parameters to a logging function that
  doesn't do string formatting.

All of these locations where found by the enhanced logcheck tool from
kubernetes/klog#297.

In some cases it reports false positives, but those can be suppressed with
source code comments.

Kubernetes-commit: edffc700a43e610f641907290a5152ca593bad79

rest/request.go

@@ -1051,13 +1051,13 @@ func truncateBody(body string) string {
 // allocating a new string for the body output unless necessary. Uses a simple heuristic to determine
 // whether the body is printable.
 func glogBody(prefix string, body []byte) {
-	if klog.V(8).Enabled() {
+	if klogV := klog.V(8); klogV.Enabled() {
 		if bytes.IndexFunc(body, func(r rune) bool {
 			return r < 0x0a
 		}) != -1 {
-			klog.Infof("%s:\n%s", prefix, truncateBody(hex.Dump(body)))
+			klogV.Infof("%s:\n%s", prefix, truncateBody(hex.Dump(body)))
 		} else {
-			klog.Infof("%s: %s", prefix, truncateBody(string(body)))
+			klogV.Infof("%s: %s", prefix, truncateBody(string(body)))
 		}
 	}
 }