ramdisk-image-create shows a failed binary dependency
ramdisk-image-create shows a failed binary dependency

This patch fixes a problem: if a binary is not found, the script
exits without a message informs what is needed (because of 'set -e').

Change-Id: I00b8917918f0e6eddf8506d6548432077eb4bf14

JioCloud/diskimage-builder,qwefi/tripleo-image-elements,CSC-IT-Center-for-Science/diskimage-builder,switch-ch/diskimage-builder,openstack/tripleo-image-elements,qwefi/tripleo-image-elements,zioproto/diskimage-builder,zioproto/diskimage-builder,NaohiroTamura/diskimage-builder,openstack/diskimage-builder,takahashinobuyuki/diskimage-builder,NaohiroTamura/diskimage-builder,agroup/tripleo-puppet-elements,openstack/tripleo-image-elements,varunarya10/diskimage-builder,agroup/tripleo-puppet-elements,rdo-management/tripleo-image-elements,agroup/tripleo-puppet-elements,openstack/diskimage-builder,citrix-openstack-build/diskimage-builder,qwefi/tripleo-image-elements,radez/tripleo-image-elements,takahashinobuyuki/diskimage-builder,CSC-IT-Center-for-Science/diskimage-builder,citrix-openstack-build/diskimage-builder,agroup/tripleo-puppet-elements,qwefi/tripleo-image-elements,varunarya10/diskimage-builder,eantyshev/diskimage-builder,rdo-management/diskimage-builder,JioCloud/diskimage-builder,rdo-management/tripleo-image-elements,qwefi/tripleo-image-elements,radez/tripleo-image-elements,eantyshev/diskimage-builder,switch-ch/diskimage-builder,rdo-management/diskimage-builder