cameraserver: clear all requests and signal mRequestSignal from RequestThread during disconnect().

This helps reduce wait time on RequestThread::join() in the following situation:

T1 calls disconnect() -> Request
T2 is in RequestThread::threadLoop -> waitForNextRequest -> mRequestSignal.wait()
which has a timeout of 50ms

The 50ms timeout is cleared if we call clear() instead of
clearRepeatingRequest().

Also call repeatingRequestEnd() HAL call from clear() for correctness.

Bug: 246214490

Test: Camera CTS
Test: Vendor Testing

Change-Id: I4e8e7309b7ee7018840e078e7346ab97d549645b
Signed-off-by: Jayant Chowdhary <jchowdhary@google.com>