added --no-disk option for RC; removed duplicated SEs

@ticoann
This patch provides/fixes two issues:
 a) it adds a new parameter to the wmagent-resource-control (--no-disk) which will drop the _Disk endpoint, so it's not going to be added into the RC database
 b) it also removes duplicated SEs in the same key (cmsName)

It was well tested this morning, while I was deploying a testbed agent.