Improve spee of nic setup in netboot initrd (bnc #893788)

With this commit the list of preferred interfaces which are
either the BOOTIF interface or the list of all detected ones
is used to run the dhcp discovery. The first successfully
discovered interface is used to setup the default gateway
and route as there can only be one
- v5.06.160 released
Allow kiwi --info to be called without root permission

There is one exception though. If the repo is an iso file
which needs to be loop mounted we still need root privileges
to call the mount system call. In such a case kiwi will
exit with a useful error message
Fixed spec file by adding missing requirements; tar and psmisc
linuxefi only exists in grub2 on x86