Fix bug SSH interactive mode

Commit b44db20 introduced a bug that broke
the SSH interactive mode. If no command is
provided, Driver.GetSSHCommand is called with
an empty string instead of no parameter.

Signed-off-by: Guillaume Giamarchi <guillaume.giamarchi@gmail.com>
Make machine name optional in CLI

For commands inspect, ip, kill and restart.
It is already implemented for the others.

Signed-off-by: Guillaume Giamarchi <guillaume.giamarchi@gmail.com>
Avoid code duplication

Signed-off-by: Guillaume Giamarchi <guillaume.giamarchi@gmail.com>
Merge pull request #101 from ggiamarchi/fix-interactive-ssh

Fix bug SSH interactive mode
Merge pull request #103 from ggiamarchi/machine-name-optional

Make machine name optional in CLI
use vpc-id and zone instead of subnet-id for ec2

Signed-off-by: Evan Hazlett <ejhazlett@gmail.com>