HWC2: Kill logspam for non-HWC virtual displays

Removes some logspam and fixes some non-errors which were reported as
errors when running a virtual display that is not backed by hardware
composer.

Test: Cherry-pick from internal branch
Bug: 30022738
Change-Id: Ie966e37d95f53bcc050eef064d24bbe26748b7fd
(cherry picked from commit 179533d1)