Remove --disable-quiet and quiet mode, default to a sane behavior

This patch is a follow-up to 1f1c2e0 which introduced the new semantics
for the very confusing quiet and silent modes.

The initial idea was to loosely follow the kernel cmdline 'quiet' option
and as a working concept this was good.  The resulting code, however,
became unnecessarily complex and the configure options impossible to
explain.

With this patch the quiet mode, and thus the --disable-quiet configure
option, is removed.  Finit now defaults to a sane behavior: services are
shown only at startup.   The --enable-silent option works like it did
before, silencing everything.

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

src/log.h

@@ -40,7 +40,7 @@
 #define  _e(fmt, args...) logit(LOG_ERR,     "%s():" fmt "\n", __func__, ##args)
 #define _pe(fmt, args...) logit(LOG_ERR,     "%s():" fmt ": %m\n", __func__, ##args)
 
-void    log_init        (int qit, int dbg);
+void    log_init        (int dbg);
 void    log_exit        (void);
 
 void    log_silent      (void);