liblights: fix some issue

1. When a notification is cleared off-screen, the LED stops pulsing
  but Xperia logo is still lit. (By adding a parameter to clear_lights_locked
  to force clear logo backlight when LED stops)

2. When offMS is 3+ times longer than onMS and pattern_duration=1
  (on 300ms, off 1000ms for WeChat) force delay 1s. See inline comments.

Change-Id: I2bf50b9b9d72cd1047061b5ea75d0a8306b27615