support multiple osd per node

[exkson]

The goal of this PR is to support the deployment of multiple OSDs per testnode. To do this,

• the number of loop devices per node is read from the configuration file
• loop devices are created using the following naming loop.
• the testnode container create_cmd is modified to dynamically include the created nodes.

With this implementation, I think each testnode will have enough devices available so that cephadm can deploy many OSDs to it if necessary.

[exkson]

This is a temporary change because exposing 5432 conflict with my local postgresql instance port. If there is no reason to expose specifically on this 5432 I think it can be a change to keep.