Set last event time to previous event batch delivery time to apps

Determination of the last event time. Currently, uses
the time that the first event in the previous batch that
was sent from hardware. This produces inconsistent timing
intervals for event delivery to apps. Now, use the time that the
previous batch was delivered to the application.

Original Author: Stephen Moore <steve.moore@motorola.com>
Signed-off-by: makarand.karvekar <makarand.karvekar@motorola.com>

Change-Id: I2a3701915702d622dc04fbf4bbd4918a9ebe8856