Revert "binder: Prevent context manager from incrementing ref 0"

This reverts commit c5665caf.

This patch was causing display hangs for Qualcomm after the 5.4.58
merge.

Bug: 166779391
Change-Id: Iaf22ede68247422709b00f059e5c4d517f219adf
Signed-off-by: Todd Kjos <tkjos@google.com>