Skip metric increment during existence check (#12763)

* Skip metric increment during existence check

Signed-off-by: Vinayak Kadam <kadamvinayak03@gmail.com>

* Adding changelog.txt

Signed-off-by: Vinayak Kadam <kadamvinayak03@gmail.com>

* Updated changelog text

Signed-off-by: Vinayak Kadam <kadamvinayak03@gmail.com>

changelog/12763.txt

@@ -0,0 +1,3 @@
+```release-note: bug
+core: Fix double counting for "route" metrics
+```

vault/router.go

@@ -535,10 +535,12 @@ func (r *Router) routeCommon(ctx context.Context, req *logical.Request, existenc
 		return logical.ErrorResponse(fmt.Sprintf("no handler for route %q. route entry not found.", req.Path)), false, false, logical.ErrUnsupportedPath
 	}
 	req.Path = adjustedPath
+	if !existenceCheck {
 		defer metrics.MeasureSince([]string{
 			"route", string(req.Operation),
 			strings.Replace(mount, "/", "-", -1),
 		}, time.Now())
+	}
 	re := raw.(*routeEntry)
 
 	// Grab a read lock on the route entry, this protects against the backend