Make Autofill PERF tests more lenient to error.

These tests were based on CTS autofill tests, where correctness is the priority
(for example, there should be no "orphan" onFillRequest() call) and the number
of UI interactions is small.

But that "correctness" model doesn't work well on PERF, because the
onFillRequest() calls are handled in the main thread and the main test loop can
make hundreds of UI calls. For example, if testFocus_autofillUsernameOnly()
doesn't set the ignored id on the password field, each focus on that field would
result in a new onFillRequest(), which is not called right away. As such, the
main loop would finish, but subsequent tests would hang until all those calls
are made.

Test: mmma -j ./frameworks/base/apct-tests/perftests/core/ &&  \
  adb install -r $OUT/data/app/CorePerfTests/CorePerfTests.apk && \
  adb shell am instrument -w -e class android.view.autofill.AutofillPerfTest \
  com.android.perftests.core/android.support.test.runner.AndroidJUnitRunner

Bug: 38345816

Change-Id: I83a311e719966dcf41e86142952075e68d0c64bf