Honor preempt_delay setting on startup.

This is a fix to honor the preempt_delay setting on power-up, or reboot, by
preventing a BACKUP router to transition to MASTER until its preempt timer
has expired.

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>
Merge pull request #35 from jonasj76/fix-preempt

Honor preempt_delay setting on startup.