network add-local: Extract absolute path for internal.sock

[matevz]

If you do

oasis net add-local rofl_node unix:internal.sock

and then

oasis net status --network rofl_node

it works, but only if you're in the same folder at the point when you added the internal.sock. When calling net add-local, it should extract the absolute path of the provided file and store that one to the config file.