FIX: get all network visualization layer ids

[thl-cmk]

Retrieve all layer IDs, not just those from the default directory

General information

The network visualization should be able to render all layers from all topology folders. Currently only the layers from the default folder will be recognized.

Bug reports

Without this change, the network visualization only recognizes the layer IDs from the default topology folder and therefore ignores all other layers in other folders. For example, if only the CDP layer is located in the default folder, the LLDP/IPv4/IPv6 in another folder will not be rendered.

Proposed changes

With this change, the network visualization reads all layer IDs from all topology folders and can then render them.