Automatic merge from submit-queue

Type define note "errNotAcceptable" should be "errUnsupportedMediaType"

In file "pkg\apiserver\errors.go", line 129:
"// errNotAcceptable indicates Content-Type is not recognized"
Here "errNotAcceptable" shuould be "errUnsupportedMediaType", thus consistent with line 131:
"type errUnsupportedMediaType struct"