Update vmware/govmomi vendor: add vapi package

Zones implementation for vSphere cloud provider needs dependencies
which are not included in current vmware/govmomi vendor. So this
update added "vapi" package to support zones.

vendor/github.com/vmware/govmomi/vim25/soap/error.go

@@ -39,7 +39,11 @@ func (s soapFaultError) Error() string {
 	msg := s.fault.String
 
 	if msg == "" {
-		msg = reflect.TypeOf(s.fault.Detail.Fault).Name()
+		if s.fault.Detail.Fault == nil {
+			msg = "unknown fault"
+		} else {
+			msg = reflect.TypeOf(s.fault.Detail.Fault).Name()
+		}
 	}
 
 	return fmt.Sprintf("%s: %s", s.fault.Code, msg)