apps: switch to absolute time labels on x-axis

Switch from displaying the elapsed time in ms to the absolute time
on the x-axis for service state graphs.  Switching from elapsed to
absolute time simplifies analysis by making it easier to correlate
log messages (with full absolute time) to the graphs (simplified
absolute time - hh:mm:ss).

Added a test covering the calculation for the log timezone offset.

TEST=checked multiple log files and ran grunt test

Change-Id: I82cc90c996ce3fc7641d70f3e9562e784be76977
5 files changed