fixed exception handling and added monotonic seeking with systemd journal IDs

Summary: added seeking via monotonic timestamps

Test Plan:
	journald_api:get_realtime_usec(Journal).
	journald_api:get_monotonic_usec(Journal).
	journald_api:seek_realtime_usec(Journal, Usec).
	journald_api:seek_monotonic_usec(Journal, Boot_ID, Usec).

compare with

	journalctl -o export

important fields:
	__REALTIME_TIMESTAMP=
	__MONOTONIC_TIMESTAMP=

Reviewers: hsychla, druss

Reviewed By: druss

CC: hwinkel, mkraemer, druss, aschultz

Differential Revision: https://review.tpip.net/D1193