CP-5960: Add tapback init.d script

Signed-off-by: Zheng Li <zheng.li@eu.citrix.com>
Reviewed-by: Chandrika Srinivasan <chandrika.srinivasan@citrix.com>
Reviewed-by: Thanos Makatos <thanos.makatos@citrix.com>
CP-5960: RPM pack the tapback init script

Signed-off-by: Zheng Li <zheng.li@eu.citrix.com>
Reviewed-by: Chandrika Srinivasan <chandrika.srinivasan@citrix.com>
Reviewed-by: Thanos Makatos <thanos.makatos@citrix.com>
Merge changes for CP-5960

Github: close #48 on xapi-project/blktap