annot create image: Image rbd/new3 does not exist

I used restapi to create a image as below, but failed and feedback as bellow:

```
[root@node11 ~]# curl --insecure --user admin:admin -d mode=create -d size=10g -d pool=rbd -X PUT http://10.10.10.10:5001/api/disk/rbd/new3
{
"message": "Image rbd/new3 does not exist"
}
```

all functions are normal in ```old version```,:
```
ceph-iscsi-cli.noarch=2.6-1.el7.centos
ceph-iscsi-config.noarch=2.5-1.el7.centos
python-rtslib.noarch= 2.1.67-1
targetcli-fb.noarch=2.1.fb48-1
tcmu-runner=1.3.0
```

I updated tools recently and now they are:
```
ceph-iscsi=3.0
rtslib-fb=-2.1.fb69
targetcli-fb=2.1.fb49
```

Start by reproducing the PUT request to /api/disk/rbd/new3 with mode=create, size=10g, and pool=rbd. Compare the behavior with the listed older and newer ceph-iscsi, rtslib-fb, and targetcli-fb versions, then trace the REST API handling of image creation. Done means the request creates the RBD image instead of returning “Image rbd/new3 does not exist.”

Written by the indexing model from the issue text.