auth_level and require_secure_login were defined in two places:
- global.c that picked it from headers and removed 'extern'
- telnetd.c that initialized it to 0
line was defined twice: in global.c and sys_term.c with a non-zero value.
Remove the definition and initialization from sys_term.c and initialize
the variable early in main().
Detected during the build of telned with Address Sanitizer (MKSANITIZER).
Reviewed by <mrg>
d9a1e5d37f