Support cache refresh without restart of ODL

In Kubernetes enivronment side load of yang models from devices that do not support ietf-netconf-monitorinig appears to be imporssible. Copying files into cache/schema on an nfs mount makes the files available in the container but upon restart of ODL a new container is created that does not see the yang files.

Need a mechanism to recreate the cache index so that the side loaded models can be preserved across container re-creates