Simplify, drop --enable-fallback-shell from configure script

Recommend using `notty` option in tty stanza instead.  See the updated
docs for details.

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

src/conf.c

@@ -737,10 +737,6 @@ int conf_reload(void)
 
 	globfree(&gl);
 
-	/* Verify config, do we have at least one TTY available? */
-	if (tty_fallback(FINIT_CONF))
-		logit(LOG_WARNING, "warning, no getty enabled on local TTYs.");
-
 	/* Mark any reverse deps as chenaged. */
 	service_update_rdeps();