OpenSL ES AudioStream.getBufferSizeInFrames() returns 0 when callback not used

[robertwu1]

Android version(s): ALL
Android device(s): ALL
Oboe version: Latest
App name used for testing: UnitTestRunner

Below is a very basic test that fails on all devices on all Android versions:

TEST_F(StreamOpenOutput, OutputForOpenSLESPerformanceModeNoneGetBufferSizeInFrames){
    mBuilder.setPerformanceMode(PerformanceMode::None);
    mBuilder.setAudioApi(AudioApi::OpenSLES);
    ASSERT_TRUE(openStream());
    EXPECT_GT(mStream->getBufferSizeInFrames(), 0);
    ASSERT_TRUE(closeStream());
}

When callbacks are not used, getBufferSizeInFrames() returns 0. This in return causes writing to the stream to never actually write.

[robertwu1]

This is an extension of #285 as #287 only fixes the callback case and not the non-callback case.