BrowsablePlayerConnector: Always remove pending players on handler

After processing a message on it's Handler, BrowsablePlayerConnector
checks if there is no pending players to call a callback with all the
result.

The code handling MSG_CONNECT_CB was calling a function with a
callback and removing the player within this callback, as it's in a
different function that the Handler#processMessage, the check to
see if it was the last player was not executed and would only
run on the next message.

The Bluetooth app also registers a MediaBrowserService and this
one usually comes last, this player doesn't have any folder so it
was removed from within the callback (results.size() == 0) and the
only message happening after that was CONNECT_TIMEOUT_MS after 10s.

This means that you would only be able to do browsing on AVRCP only
if you opened AVRCP 10s after the startup of the stack.

pts-bot was triggering both cases, connecting before and after 10s
which made the test flaky.

Test: atest pts-bot:AVRCP/TG/MCN/CB/BI-01-C --iterations 100
Fix: 287463103
Change-Id: I8339a2e58a4880e6cfd0ebc2f2f2653da97853da