Bluetooth: mgmt: Move service cache setting to a more sensible place

Since we can now add UUIDs when powered off we don't really need to
always use the service cache to avoid large bursts of HCI commands.
Instead, the only important use case is when we're already powered and
user space starts to initialize itself. This can be easiest detected by
a "clear UUIDs" operation which is where this patch moves the service
cache setting.

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Acked-by: Marcel Holtmann <marcel@holtmann.org>