<fix>[vm]: check existing mirror job
<fix>[vm]: check existing mirror job

Resolves: ZSTAC-46757

Change-Id: I62626473667670706667736569736c6279786e73

Signed-off-by: Qun Li <1ea81f54854048d0a4d4fd61caceabb2a843281c@zstack.io>

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