Replace RTC with monotonic clock

:Release Notes:
Made sleepd more tolerant to RTC-less devices.

:Detailed Notes:
- added special monotonic reference clock to count time with
  notification on time change
- replace RTC reference clock with new special monotonic clock
- extracted quee_next_wakeup from _queue_next_timeout to make clear
  when we want to setup RTC wakeup alarm
- by default disable code that asks RTC for wakeup on each event
  processing iteration

:Testing Performed:
- desktop build

:QA Notes:

:Issues Addressed:
[GF-6704] sleepd daemon looks unhappy

Open-webOS-DCO-1.0-Signed-off-by: Nikolay Orliuk <nikolay.orliuk@lge.com>

Change-Id: I451edd99739f62a6e429c65342590caf9526ac62
Reviewed-on: https://g2g.palm.com/3860
Reviewed-by: Keith Derrick <keith.derrick@lge.com>
Reviewed-by: Build Verification
Tested-by: Keith Derrick <keith.derrick@lge.com>