The value of tmnxSysRollbackFileDelete specifies whether to delete
the rollback file specified by tmnxSysRollbackIndex.
When SET to the value of 'doAction' the system will delete the
rollback file specified by tmnxSysRollbackIndex.
This variable must be set along with tmnxSysRollbackIndex to specify
the specific rollback file to delete.
An SNMP GET request on this object should return 'notApplicable'.