[Media ML] Sync with original implementation

Originally, a volume key long press listener would have been called
for the first ACTION_DOWN KeyEvent with repeat count equal to 0, but
the new implementation does not call it.
This CL fixes the current implementation to match the original
implementation.

Bug: 157988289
Test: manually
Change-Id: I563215fc522e952412ebbae1ddaa1a6b1b646c53