Switch Checkpoint health sleep time to ms.

This changes the property from microsecond to milliseconds, as we don't
need that sort of precision here. Also switches from using ulseep, which
has been removed from POSIX, to nanosleep.

Test: Builds, Boots, Times
Change-Id: Iefbaf8489ba05d8d688542fd7d4305efb980e701
1 file changed