<fix>[vm]:fix err description when change vcpu&mem
<fix>[vm]:fix err description when change vcpu&mem

1. fix err description when changing a running vm vcpu num and mem size,
whether Instance Offering Online Modification is on or not;

Resolves: ZSTAC-48575

Change-Id: I627277616d7967667a6968776b64716d65716567

zstackio/zstack-utility,zstackio/zstack-utility,zstackio/zstack-utility