Start device scan even if device is already discovered.

The SuggestedDeviceConnectionManager should ensure that scan is always
active during the connection attempt, which means that `startScan`
should be called before `connect` and `stopScan` should be called only
after the connection attempt is finished.

Fix: 445443975
Test: atest SuggestedDeviceConnectionManagerTest
Flag: com.android.media.flags.use_suggested_device_connection_manager
Cherrypick-From: https://googleplex-android-review.googlesource.com/q/commit:76d45a5a5a48166db1874d04711ee0422057fe09
Merged-In: Id5248da30fc035f5946f18db5b3405a131a9f4cf
Change-Id: Id5248da30fc035f5946f18db5b3405a131a9f4cf