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/models/mullvad.go

@@ -3,10 +3,10 @@ package models
 import "net"
 
 type MullvadServer struct {
+	IPs         []net.IP
 	Country     MullvadCountry
 	City        MullvadCity
 	Provider    MullvadProvider
 	Owned       bool
-	IPs         []net.IP
 	DefaultPort uint16
 }