Mark flaky presubmit tests as @Postsubmit

Previously tests passing <95% of the time were considered flaky. Now we
mark any test passing <99% of the time as flaky.
Also increase wait time before assert in switchToCdma which was failing
inconsistently.

Bug: 31041734
Change-Id: Ibb353c99049b049f57d0f67b5027278d58c5f69b