gatt_attr: Read GATT Server supported features in a sequence

With this patch Android reads Server Supported Features and writes
Client supported featuers after discovery.

From now on, Eatt will not trigger GATT read if Server Supported Feature
value is already known.

This helps to pass GATT/CL/GAN/BV-02-C
Bug: 236083555
Test: atest Bluetooth InstrumentationTests
Tag: #stability

Change-Id: I41f027a768a57c4885e057d4086236a45d20f573