guard against empty input
limit the number of retries
Creating a sub-project called opennms-rrd-model

This package is going to contain all RRD-ORM related classes and
utilities created for manipulating and combining the Dump/Xport
representations of RRDs and JRobin.

core/upgrade has been upgraded to use opennms-rrd-model
Merge remote-tracking branch 'origin/1.12' into upgrade-tools-1.12