Fix the bogus configs default-constructed as a2dp configs

When the xml file contains the "invalid" entry in the scenario record,
which do not refer to any valid config in the 'configurationList`
section, the invalid, default constructed codec configuration (a2dp codec)
was created.

Bug: 319090769
Test: atest VtsHalBluetoothAudioTargetTest
Change-Id: I19b7d1af81e5f2be3fb7261fba8781b3dc47fa12