Revert "hardware/qcom/display: Remove glfinish call"

This reverts commit 95bc6a5c6dd76a432baaa6554abd0f4f7ca481f1.

Without glFinish(), in few corner cases; application is trying to
lock the buffer for write, while the read lock is still held.

CRs-Fixed: 430212

Change-Id: I9e3a22ca3496ef42e8dce5d565bcfe79fd427a4d