No vdi merge through smb

src/api/vm.coffee

@@ -498,6 +498,8 @@ rollingDeltaBackup = $coroutine ({vm, remote, tag, depth}) ->
     throw new Error "No such Remote #{remote}"
   if not _remote.enabled
     throw new Error "Backup remote #{remote} is disabled"
+  if _remote.type == 'smb'
+    throw new Error "Delta Backup is not supported for smb remotes"
   return yield @rollingDeltaVmBackup({
     vm,
     remoteId: remote,

src/xo-mixins/backups.js

@@ -267,6 +267,9 @@ export default class {
   }
 
   async _mergeDeltaVdiBackups ({remote, dir, depth}) {
+    if (remote.type === 'smb') {
+      throw new Error('VDI merging is not available through SMB')
+    }
     const backups = await this._listVdiBackups(remote, dir)
     let i = backups.length - depth