cyclades: Tool for checking Cyclades update path

Create a tool for checking the status of Cyclades update path, which
includes Ganeti, AMQP, snf-ganeti-eventd and snf-dispatcher. The tool is
created as part of the snf-dispatcher and can be used by passing the
'--status-check' option.

The tool sends a 'status-check' message to the running snf-dispatcher
process (via AMQP) and then waits to get the status report from an
exclusive queue. Respectively, the snf-dispatcher uses the Ganeti RAPI
client to add a special tag to each Ganeti cluster (in dry-run mode),
which will trigger snf-ganeti-eventd to send a heartbeat message to the
AMQP broker. Dispatcher collects all these message and sends the status
report back to the tool that triggered the status check.

Closes #23