Camera: Fix memory leak if malformed face data is received

The unparceling code for face metadata in API1 dynamically allocates
a camera_metadata structure, and a recent fix forgot to delete that
structure in an error path.

Fix this by making the metadata structure statically allocated; it's
tiny anyway.

Test: atest CtsCameraTestCases
Bug: 155512103
Change-Id: I9b81cdb3ab47c7b6c94c6ed65213ddafef529dc9