Fix /data dir creation, 'tlsdated' service class.

/data is not guaranteed to be mounted when 'boot' triggers.
'post-fs-data' guarantees that. Also, move the daemon to class
'late_start', since post-fs-data will not happen in time for class
'main'.

Bug: 25122706
Change-Id: I2a636df27461ebc21270dd2380c6d5d69f253d3d