gatt: Fix incorrect GATT confirmation on indication

If there is many GATT users, Android sends indication to all the users
and expects confimation.
Without this fix, we could endup sending multiple Confirmation to remote
device on single Indication - which is wrong.

This patch fixes this.
Found during PTS HAP testing.

Bug: 238171211
Test: atest BluetoothInstrumentationTests
Test: PTS
tag: #feature
Change-Id: Ieef9a0f3448ce8529624e777282e857a7f206c00