Merge pull request kubernetes#60838 from CaoShuFeng/amdission_control…

…ler_glog

Automatic merge from submit-queue. If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

log enabled admission controller in order

After switching to --enable-admission-plugins/--disable-admission-plugins, some admission controller may start silently. And these admission controllers may modify or forbid objects. This pull request does a lot of help for admin to trouble shooting.

/assign @hzxuzhonghu @sttts 

**Release note**:
```release-note
NONE
```

staging/src/k8s.io/apiserver/pkg/admission/plugins.go

@@ -23,6 +23,7 @@ import (
 	"io/ioutil"
 	"reflect"
 	"sort"
+	"strings"
 	"sync"
 
 	"github.com/golang/glog"
@@ -144,6 +145,9 @@ func (ps *Plugins) NewFromPlugins(pluginNames []string, configProvider ConfigPro
 			}
 		}
 	}
+	if len(pluginNames) != 0 {
+		glog.Infof("Loaded %d admission controller(s) successfully in the following order: %s.", len(pluginNames), strings.Join(pluginNames, ","))
+	}
 	return chainAdmissionHandler(handlers), nil
 }