Support more CVMFS paths

[duncanmmacleod]

Currently stashcp will check locally against /cvmfs/stash.osgstorage.org to see if CVMFS already has the file:

osdf-client/handle_cvmfs.go

Lines 12 to 14 in 8f6fff3

	func download_cvmfs(sourceFile string, destination string, payload *payloadStruct) (int64, error) {
	//Check if file is available in cvfms
	var cvmfs_file string = path.Join("/cvmfs/stash.osgstorage.org", sourceFile)

Is it reasonable to add more CVMFS repository paths to that list to support other uses (e.g. IGWN)?