wip: set default snapshot type to images

This is to run a full integration test with disk image snapshot.
This commit is not part of the PR. Revert after all tests pass.

Author: luohao

pkg/common/parameters.go

@@ -136,7 +136,7 @@ func ExtractAndDefaultParameters(parameters map[string]string, driverName string
 func ExtractAndDefaultSnapshotParameters(parameters map[string]string) (SnapshotParameters, error) {
 	p := SnapshotParameters{
 		StorageLocations: []string{},
-		SnapshotType:     DiskSnapshotType,
+		SnapshotType:     DiskImageType,
 	}
 	for k, v := range parameters {
 		switch strings.ToLower(k) {

pkg/common/parameters_test.go

@@ -189,7 +189,7 @@ func TestSnapshotParameters(t *testing.T) {
 			parameters: nil,
 			expectedSnapshotParames: SnapshotParameters{
 				StorageLocations: []string{},
-				SnapshotType:     DiskSnapshotType,
+				SnapshotType:     DiskImageType,
 			},
 			expectError: false,
 		},