kubeadm: do not use github.com/blang/semver in app/preflight

Usage of github.com/blang/semver is not needed and
k8s.io/apimachinery/pkg/util/version should be used instead
for semantic version parsing and version comparison.

Author: neolit123

cmd/kubeadm/app/preflight/BUILD

@@ -31,7 +31,6 @@ go_library(
         "//staging/src/k8s.io/apimachinery/pkg/util/sets:go_default_library",
         "//staging/src/k8s.io/apimachinery/pkg/util/version:go_default_library",
         "//vendor/github.com/PuerkitoBio/purell:go_default_library",
-        "//vendor/github.com/blang/semver:go_default_library",
         "//vendor/github.com/pkg/errors:go_default_library",
         "//vendor/k8s.io/klog:go_default_library",
         "//vendor/k8s.io/utils/exec:go_default_library",

cmd/kubeadm/app/preflight/checks.go

@@ -35,7 +35,6 @@ import (
 	"time"
 
 	"github.com/PuerkitoBio/purell"
-	"github.com/blang/semver"
 	"github.com/pkg/errors"
 	netutil "k8s.io/apimachinery/pkg/util/net"
 	"k8s.io/apimachinery/pkg/util/sets"
@@ -65,7 +64,7 @@ const (
 )
 
 var (
-	minExternalEtcdVersion = semver.MustParse(kubeadmconstants.MinExternalEtcdVersion)
+	minExternalEtcdVersion = versionutil.MustParseSemantic(kubeadmconstants.MinExternalEtcdVersion)
 )
 
 // Error defines struct for communicating error messages generated by preflight checks
@@ -722,12 +721,12 @@ func (evc ExternalEtcdVersionCheck) Check() (warnings, errorList []error) {
 			continue
 		}
 
-		etcdVersion, err := semver.Parse(resp.Etcdserver)
+		etcdVersion, err := versionutil.ParseSemantic(resp.Etcdserver)
 		if err != nil {
 			errorList = append(errorList, errors.Wrapf(err, "couldn't parse external etcd version %q", resp.Etcdserver))
 			continue
 		}
-		if etcdVersion.LT(minExternalEtcdVersion) {
+		if etcdVersion.LessThan(minExternalEtcdVersion) {
 			errorList = append(errorList, errors.Errorf("this version of kubeadm only supports external etcd version >= %s. Current version: %s", kubeadmconstants.MinExternalEtcdVersion, resp.Etcdserver))
 			continue
 		}