GraphicsTracker: detach after allocate from PlaceHolderSurface

PlaceHolderSurface only allocates buffers after stop()/release(). So
PlaceHolderSurface supports limitted number of buffers to allocate,
since stop()/release() request should be processed as soon as possible.

But certain HALs allocates considerably large number of buffers after
stop()/release() being requested. In order to cope with this wild
behaviors of HAL, detach buffer(s) after allocate.

BYPASS_IGBP_IGBC_API_REASON=clean up after warren buffer flag on

Bug: 376367859
Test: presubmit
Flag: EXEMPT bugfix
Change-Id: I511f863d6b5ae6d534322e3936fec62866752268