Output current times in ISO-8601 format

ISO-8601 seconds based representation is used in various dumpsys logs
related to time / time zone detection. This helps by providing a clear
record of what "now" was without resorting to a calculator / other
tools.

Bug: 188174391
Test: adb shell dumpsys time_detector
Change-Id: Ie6fc0f4e78c1284b0ed41e1cfbb6cc690556693a