The global lock is too restrictive

[poncovka]

We would like to be able to work with different copies of Blivet at the same time, but currently it is not possible, because Blivet uses one global lock for every object it owns. It doesn't cause any problems at this moment, because Anaconda is designed to wait for all the long-term storage-related jobs to be done before we do anything else with the storage. However, it affects the usability of our DBus Storage module. We call reset on a new copy of Blivet in a separate thread, but DBus calls can be blocked by the global lock until the reset is finished even though they use a different copy of Blivet at that moment.