LeAudio: Fix redundant AIDL call with software encoding

When using software encoding the AIDL call for the audio set
configuration fails and we fall back to local configurations source.
On software path we should use local configuration and not call the AIDL
interface at all.

Bug: 374933885
Bug: 313054645
Test: atest bluetooth_le_audio_codec_manager_test
Flag: EXEMPT; bug fix covered with unit tests
Change-Id: I5f26a4326594a54228ee9a33835c12934101afc7