This commit adds some better handling around the snapshot restore and
delete commands for the virtualbox provider. If a user attempts to restore from
a vm that does not exist, instead of exiting 0 it will raise an
exception saying the virtual machine has not been created yet.
Addtionally, if a user attempts to restore from a snapshot id that does
not exist, instead of printing a complicated exception from the
virtualbox cli tool, it prints a more useful error message telling the
user that the snapshot does not exist.
Prior to this commit, if a user attempted to use the `vagrant snapshot
save` or `vagrant snapshot list` commands on a vm whose provider did not
support snapshots, it would simply print a warning. This commit changes
that behavior by instead raising an error.
Prior to this commit, the vagrant snapshot plugin would save snapshots
with existing names which lead to duplicate snapshot names being saved.
This commit fixes that by checking to see if the given snapshot name
already exists and if so, fails telling the user the given snapshot name
already exists. If a user passes a --force flag, vagrant will first
delete the existing snapshot, and take a new one with the given name.
Chris Roberts
Brian Cain
Mitchell Hashimoto