Fix LE scan breaks

Currently, we would periodically lower the LE scan parameters during
device discovery triggered from Settings. This would result in one
second breaks. If device is discovered on Classic transport during such
break, but not on LE transport, we can pick bad transport for pairing.

Bug: 316885813
Bug: 315064540
Test: go to "pair new device" in Settings, tap on device quickly after
      it shows on list. verify transport used for bonding.
Change-Id: I2b5c5d84af021c9a42c3f04497daa3e034d50e8f