Use mock to build rpm packages and preparing initramfs

1) (docker) sudo command was removed from docker.
   User is now placed in docker group and can access docker
   socket without sudo
2) (rpm) rpm packages now build using mock without sudo
3) (bootstrap) initramfs is now prepared in mock env

Notes:
- Ask user to relogin, in order to correctly process group membership
- Fix issue with multistrap version
- Improve nodejs support and installation
- Old files saved for checking and should be removed in future
- Fix lrzip periodical issue with infinite loop (removed -U option)
- Ensure bc package is present (for building img file)

ToDo:
- Fix sudo for createchroot.mk for ubuntu
- Fix sudo for building img targets
- provide mock environment for building OpenStack packages

Change-Id: I9e82c87e950f5c95d301a14177c649d9dc2511e6