fix disk driver type in manager backup init template

[koval4ukav]

Description

This PR is to fix an issue in the backup init template /dev/sdb => /dev/vdb, as with the current init file, oncet the topology backup is done, the restore of the Manager from that backup will not be successful, it will be stuck:

Welcome to Viptela CLI
admin connected from 127.0.0.1 using console on Manager01
1) COMPUTE_AND_DATA
2) DATA
3) COMPUTE
Select persona for vManage [1,2 or 3]: 

Type of Change

• Bug Fix
• New Feature
• Breaking Change
• Refactor
• Documentation
• Other (please describe)