failure to load sumocfg in subfolder from command line

[namdre]

regression in 1.26.0

i.e. netedit subfolder/test.sumocfg causes

Error: File 'subfolder/subfolder/net.net.xml' is not accessible (No such file or directory).

• loading config with dialog is not affected
• cd-ing into the folder and loading the config from there also works
• loading a network file from a subfolder also works
• loading a .netecfg from a subfolder also works

[namdre]

regression via #17446: the second call to relocateFiles adds the subfolder prefix again and thus creates an invalid path.

[palvarezlopez]

Fixed in 49ec0de