Re-remove CONNECTIVITY_CHANGE_DELAY and supporting functions.

Since optimistic addresses are useable upon kernel notification
there is no need for this extra connectivity delay.

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This functionality was originally submitted in ag/572619.  Owing
to issues with bind()ing to optimistic addresses (see b/18609055)
this was reverted in ag/598673.

This reverts the revert.  :-)

Bug: 17769720
Change-Id: Ibee490b2af72050693b6bd748193f51e312ca527