hsqueeze: fix position of option in gnt-node power

hsqueeze can produce a shell script with the commands to squeeze
the cluster; in the script, fix the position of the '-f' option
in the 'gnt-node power' command.

Signed-off-by: Klaus Aehlig <aehlig@google.com>
Reviewed-by: Jose Lopes <jabolopes@google.com>