init.rc: enable ledtrig-transient support for vibrator

This change makes the init process to always attempts to enable
transient trigger for vibrator. This allows the exported properties to
change the ownership later at the on boot stage.

Test: device vibrates with the driver supports ledtrig-transient

Change-Id: If5eb7b7feaefe803f2ead634fbe4fc7b48da84ea
Signed-off-by: David Lin <dtwlin@google.com>