ctld: Some bool-related cleanups

• Convert a few variables from int to bool

• Return bool instead of inverted 0/1 from configuration parsing functions and the auth check functions

• Invert the existing dont_daemonize bool into a daemonize boolx

Reviewed by: asomers
Sponsored by: Chelsio Communications
Differential Revision: https://reviews.freebsd.org/D48928