Handle full hostname when computing host tag on GCE

The current code assumes the full domain name will not be included,
which is not always the case. This patch adds support for computing the
host tag from a fully qualified domain name.

pkg/cloudprovider/gce/gce.go

@@ -445,6 +445,7 @@ func (gce *GCECloud) CreateTCPLoadBalancer(name, region string, externalIP net.I
 // This is kind of hacky, but the managed instance group adds 4 random chars and a hyphen
 // to the base name.
 func (gce *GCECloud) computeHostTag(host string) string {
+	host = strings.SplitN(host, ".", 2)[0]
 	return host[:len(host)-5]
 }
 

pkg/cloudprovider/gce/gce_test.go

@@ -50,6 +50,10 @@ func TestGetHostTag(t *testing.T) {
 			host:     "gke-test-ea6e8c80-node-8ytk",
 			expected: "gke-test-ea6e8c80-node",
 		},
+		{
+			host:     "kubernetes-minion-559o.c.PROJECT_NAME.internal",
+			expected: "kubernetes-minion",
+		},
 	}
 
 	gce := &GCECloud{}