le_audio: Don't set group as inactive when device remains connected

In OnLeAudioDeviceSetStateTimeout, when target state was Idle, and some
of the devices in group reached it, they won't be disconnected. Because
of that, group has still connected devices and shall not be set as
inactive.

Bug: 379000118
Flag: EXEMPT, regression verified with unit test
Test: atest --host --no-bazel-mode bluetooth_le_audio_client_test
Change-Id: I1dfe24ed39ca7d9e9cc016be935957cef134f9fc