C2SoftFlacEnc: Send single frame per output by using cloneAndSend

Bug: 169310292
Test: atest CtsMediaV2TestCases:AudioEncoderTest
   CtsMediaV2TestCases:CodecEncoderTest
   CtsMediaEncoderTestCases:EncoderTest
   CtsMediaCodecTestCases:MediaCodecTest
   VtsHalMediaC2V1_0TargetAudioEncTest
(cherry picked from https://android-review.googlesource.com/q/commit:28f645061bb42cc3d68d6fab2a0015c1b0d82cb2)
Merged-In: Iecb2f4b18594a50d5e64ef271713e6676a319b93
Change-Id: Iecb2f4b18594a50d5e64ef271713e6676a319b93