Fix GATT Server disconnecting for no reason

Connections created by GAP profile should be ephemeral, and not
interfere with the connection timeout.

When a device is bonded, listing services through DM would cause a
DM APP to create a connection, and later to disconnect. This causes
connection to timeout. In case a device was already connected, this
should not happen.

Bug: 34951749
Test: manual
Change-Id: Iad04fd9eed4c664f35131442e3f83a704497a067