Fix conflicting rspec shared example names
Change Mirror middleware execution sequence to run after provisioning

The VM::Provision middleware defers the provisioning to run at the end
of the stack, so the Mirror middleware needs to defer its own execution
to run once the provisioning has completed.
Fix syntax errors, abort on any thread exception
Missing base method in GuestInstall
Run SFTP event loop following each changeset

When used asynchronously, Net::SFTP doesn't actually make any transfers
until you call the loop command or issue a synchronous request. The sync
changes action needs to explicitly call finish_transfers after every
changeset to cause it actually to transfer the files.