Bluetooth: Fix clearing discovery type when stopping discovery

This patch prevents resetting of discovery type while stopping
discovery, since otherwise the wrong type might be send in case of
discovery failure. It also doesn't matter that we are "lazy" with
updating the type since it is anyway reset when starting discovery again
and it's not needed to know the current discovery state.

Signed-off-by: Hemant Gupta <hemant.gupta@stericsson.com>
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>