Fix processing of asterisk.conf debug=yes.

The code which reads asterisk.conf supports processing the debug
option with ast_true, but ast_true returns -1.  This causes debug
to still be off, convert to 1 so debug will be on as requested.

ASTERISK-25042
Reported by: Corey Farrell

Change-Id: I3c898b7d082d914b057e111b9357fde46bad9ed6