Description of problem:

It should be possible to perform multiple copy operations simultaneously for a template disk. This can be achieved by removing the read lock for template disks. 

This can make a significant improvement for shortening the time it takes to copy a template disk to several storage domains, especially for large environments with many storage domains.

For example, for our day to day work in RHV QE automation, this operation takes much of our environments preparations, where we build environments with ~10 storage domains and we need a template disk to be copied to all of them for VM creation from it on each domain.