Follow symlink for elements
Follow symlink for elements

This allow custom elements to be added with symlink. Without -follow
a symlinked element is valid but scripts in *.d directory aren't used.

Change-Id: If50b7d9c3b1f6fe278c28488146709efe5cf065f
Closes-Bug: 1461124

zioproto/diskimage-builder,zioproto/diskimage-builder,openstack/diskimage-builder,openstack/diskimage-builder,CSC-IT-Center-for-Science/diskimage-builder,takahashinobuyuki/diskimage-builder,CSC-IT-Center-for-Science/diskimage-builder,switch-ch/diskimage-builder,takahashinobuyuki/diskimage-builder,switch-ch/diskimage-builder,rdo-management/diskimage-builder,rdo-management/diskimage-builder