Guard against racy ComposerClient reconnection

The hardware composer service has a rule that only one client can be
connected at a time. The surface flinger process, when transitioning
composer ownership from surface flinger to vr flinger, will destroy the
current client on one thread and create a new client on another
thread. Although surface flinger ensures that these events happen in the
expected sequence (delete then create), the requests sometimes land in
the hardware composer service in inverted order, causing the creation
request to fail with an error.

Instead of failing with an error, block for a brief period (1 second)
until the existing client is removed, then proceed to initialize the new
client. This gives us enough time to ensure an inverted
creation/destruction order doesn't cause client creation to fail, while
avoiding a deadlock if the existing client is never destroyed.

Bug: 62925812

Test: - Transitioned to/from vr flinger hundreds of times, and confirmed
I no longer see sporadic composer client creation failure due to an
already existing client.

- Ran the vts graphics composer tests and confirmed they all pass.

Change-Id: I40be1fb0cb3d42ddb5a9fc159188886e9f5b6267