Description of problem:
Block volumeMode PVC prebound a Filesystem volumeMode PV, bound failed as expected, but event message is not clear.

Version-Release number of selected component (if applicable):
oc v3.9.0-0.20.0
openshift v3.9.0-0.20.0
kubernetes v1.9.1+a0ce1bc657


How reproducible:
Always

Steps to Reproduce:
1. Create a Filesystem volumeMode PV
2. Create a Block volumeMode PVC prebound the PV created above
3. Check the PVC and PV

Actual results:
PVC is not bound to PV, but event message is not correct.
Warning  VolumeMismatch  5s    persistentvolume-controller  Volume's size is smaller than requested or volume's class does not match with claim

Expected results:
Volume's volumeMode does not match with claim？

Additional info:
# cat pv-fs.yaml 
apiVersion: v1
kind: PersistentVolume
metadata:
  name: fs-pv
spec:
  capacity:
    storage: 5Gi
  accessModes:
    - ReadWriteOnce
  volumeMode: Filesystem
  persistentVolumeReclaimPolicy: Retain
  fc:
    targetWWNs: ["500a0981891b8dc5", "500a0981991b8dc5"]
    lun: 2
    readOnly: false

# cat pvc-block.json 
{
    "apiVersion": "v1",
    "kind": "PersistentVolumeClaim",
    "metadata": {
        "name": "claim-block"
    },
    "spec": {
        "accessModes": [ "ReadWriteOnce" ],
        "volumeName" : "fs-pv",
        "volumeMode" : "Block",
        "resources": {
            "requests": {
                "storage": "5Gi"
            }
        }
    }
}

# oc describe pvc
Name:          claim-block
Namespace:     piqin
StorageClass:  
Status:        Pending
Volume:        fs-pv
Labels:        <none>
Annotations:   <none>
Finalizers:    []
Capacity:      0
Access Modes:  
VolumeMode:    Block
Events:
  Type     Reason          Age   From                         Message
  ----     ------          ----  ----                         -------
  Warning  VolumeMismatch  5s    persistentvolume-controller  Volume's size is smaller than requested or volume's class does not match with claim