Reduce the health check timeout (2/n)

b/143035398 #3 shows the network stack will pass health check anyway
even there is not internet connected. We have to reduce the timeout and
finish the test before the health check is passed.

Bug: 143035398
Test: atest StagedRollbackTest
Change-Id: I39a84b06a19648a3ec19c5f334bed9ef4bce1533