For validation off case, do NOT switch data until new conn is up.

For validation off data switch, we will delay to tear down the old
connection until either 1) the new connection is brought up 2) new
connection failed to bring up in 2 seconds.

This is to shorten the disconnect gap during the switch.

Bug: 140070796
Test: unittest
Change-Id: I555f4d8d900fdd081738f3db8b02fb2728a3d88c