add DHCP lease folders for Ubuntu
add DHCP lease folders for Ubuntu

Add "/var/lib/dhcp/*" to the search path for Ubuntu; tested under
Ubuntu Precise and Trusty, not yet with newer releases.

DaanHoogland/cloudstack,wido/cloudstack,resmo/cloudstack,resmo/cloudstack,jcshen007/cloudstack,wido/cloudstack,GabrielBrascher/cloudstack,DaanHoogland/cloudstack,resmo/cloudstack,jcshen007/cloudstack,wido/cloudstack,wido/cloudstack,GabrielBrascher/cloudstack,jcshen007/cloudstack,jcshen007/cloudstack,DaanHoogland/cloudstack,GabrielBrascher/cloudstack,resmo/cloudstack,DaanHoogland/cloudstack,DaanHoogland/cloudstack,jcshen007/cloudstack,GabrielBrascher/cloudstack,jcshen007/cloudstack,resmo/cloudstack,jcshen007/cloudstack,wido/cloudstack,GabrielBrascher/cloudstack,wido/cloudstack,wido/cloudstack,DaanHoogland/cloudstack,resmo/cloudstack,DaanHoogland/cloudstack,resmo/cloudstack,GabrielBrascher/cloudstack,GabrielBrascher/cloudstack