Fix SurfaceSyncGroupTests

SurfaceSyncGroupTest was using a stub transaction for SurfaceSyncGroup,
but was not resetting it to the real Transaction when the test was
complete. This made the following test that was expecting to use real
Transactions fail.

Fixes: 279141968
Test: SurfaceSyncGroupTest SurfaceSyncGroupTests
Change-Id: Ifa1122ff9d74c8850b8c46216846a4e1b73f4c1c