Do not assume device_type from non-connectable advertisting packets

which omit flags entirely.

Non-connectable device may omit the flags section entirely, and no
assumptions should be made about the flag values in that case (CSSv10,
1.3.1). Currently, we will assume the device_type to be DUMO in that
case, which is incorrect. Prevent this by only setting device_type when
the flags are present or the packet is connectable.

Bug: 194397272
Test: Tested with partner device and verified that incorrect attempted
BT Classic connections are eliminated.
Tag: #compatibility

Change-Id: Ia448abf3fb1c0ee3cdae8133048043ecf2c8b9ff