le_audio: Don't proceede when GATT read invalid status is received

A gatt read response with non valid and out of sync status should
not trigger storying and proceeding to connected state of device.
Informing about connected device leads to invalid behavior e.g. not
exposing indirectly PACS/ASCS attribute values.

Tag: #feature
Bug: 304854941
Test: atest UnicastTest#DisconnectAclBeforeGettingReadResponses
Change-Id: Ifabbd97f3fa18f88b3d21592f6c6a3de55289028