BUG/MINOR: wdt: do not return an error when the watchdog couldn't be enabled

On operating systems not supporting to create a timer on
POSIX_THREAD_CPUTIME we emit a warning but we return an error so the
process fails to start, which is absurd. Let's return a success once
the warning is emitted instead.

This may be backported to 2.1 and 2.0.

src/wdt.c

@@ -156,7 +156,7 @@ int init_wdt_per_thread()
  fail1:
 	ti->wd_timer = TIMER_INVALID;
 	ha_warning("Failed to setup watchdog timer for thread %u, disabling lockup detection.\n", tid);
-	return 0;
+	return 1;
 }
 
 void deinit_wdt_per_thread()