Prevent switchHoldingAndActive() from being called twice.

There's a big old comment in the code that I added that has much more
information that I'm going to put here. This fixes an issue where we
were calling switchHoldingAndActive() too many times.

Bug: 17209905
Change-Id: I4aa1f2174f897f2f4d9f5464915b98a892b51618
1 file changed