Bluetooth: Pause service discovery for suspend

Just like MGMT_OP_START_DISCOVERY, we should reject
MGMT_OP_START_SERVICE_DISCOVERY with MGMT_STATUS_BUSY when we are paused
for suspend.

Signed-off-by: Abhishek Pandit-Subedi <abhishekpandit@chromium.org>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>