Fix the code responsible for reattaching shared directories after VMs
have been exported.
For OVA export:
- use saved share names instead of default name (for the sake of
correctness; it is unlikely that a user will change the name)
For dir export:
- save and reattach shared directories after export
Change-Id: I79162c1ec788aa1d89104aa92aebeae2bb05adf5