Golangcilint in build pipeline and fix lint errors

- Fix bad permissions bits for files
- VPNSP is 'private internet access' instead of 'pia' (retro compatible)
- Check errors of deferred unsetEnv functions in params package
-  Other lint errors fixing and code simplifications

internal/splash/splash.go

@@ -11,7 +11,7 @@ import (
 )
 
 // Splash returns the welcome spash message
-func Splash(paramsReader params.ParamsReader) string {
+func Splash(paramsReader params.Reader) string {
 	version := paramsReader.GetVersion()
 	vcsRef := paramsReader.GetVcsRef()
 	buildDate := paramsReader.GetBuildDate()