Remove unused method from Ubuntu.py

Signed-off-by: Chris Lalancette <clalancette@gmail.com>
Remove unused arguments from test_ssh_connection

Signed-off-by: Chris Lalancette <clalancette@gmail.com>
Move ssh_execute_command and scp_copy_file into Linux.py

It wasn't used anywhere else anyway.

Signed-off-by: Chris Lalancette <clalancette@gmail.com>
Make sure to close the object, not the underlying fd.

Otherwise, we get an error later when the garbage
collector tries to close out the file descriptor.

Signed-off-by: Chris Lalancette <clalancette@gmail.com>