s3: adjust permission for HEAD bucket operation

fix https://github.com/chrislusf/seaweedfs/issues/2417#issuecomment-958391856

weed/s3api/s3api_server.go

@@ -66,7 +66,7 @@ func (s3a *S3ApiServer) registerRouter(router *mux.Router) {
 		// HeadObject
 		bucket.Methods("HEAD").Path("/{object:.+}").HandlerFunc(track(s3a.iam.Auth(s3a.HeadObjectHandler, ACTION_READ), "GET"))
 		// HeadBucket
-		bucket.Methods("HEAD").HandlerFunc(track(s3a.iam.Auth(s3a.HeadBucketHandler, ACTION_ADMIN), "GET"))
+		bucket.Methods("HEAD").HandlerFunc(track(s3a.iam.Auth(s3a.HeadBucketHandler, ACTION_READ), "GET"))
 
 		// CopyObjectPart
 		bucket.Methods("PUT").Path("/{object:.+}").HeadersRegexp("X-Amz-Copy-Source", `.*?(\/|%2F).*?`).HandlerFunc(track(s3a.iam.Auth(s3a.CopyObjectPartHandler, ACTION_WRITE), "PUT")).Queries("partNumber", "{partNumber:[0-9]+}", "uploadId", "{uploadId:.*}")