fix call/call-ssid locking issue

Fix the situation where GB7DXC exists and is locked out and $allowmultiple
is active than GB7DXC-5 logs in and is locked by dint of GB7DXC's locked
status and ignores GB7DXC-5's unlocked status.

Run convert-users-v3-to-v4.pl automatically if there are no users.v4[.o/.n]
files present in local_data or data. Then copy users.v4 to users.v4,n and
do an export_users, creating users_json.

File user export so that it actually works!