Fix failing FragmentReplaceTest test.

This test was changed to work with a broken @UiThreadTest
which made these tests work on non-ui thread. @UiThreadTest just
got fixed now causing these tests to fail as we were calling
runOnMainSync that requires to be called off the main thread.

Bug:30307969
Change-Id: I14871ed755c65f6f5fb3bf3e9da94b8a21c3a4de
1 file changed