Fix several bugs in synchronization tests

Fix several bugs in synchronization tests

 * Tests were mixing default device and test-specific device objects,
resulting in use of objects created from one device with another device.

 * Tests were using DeviceInterface of default device with test-specific
device objects, leading to crashes when layers were enabled.

 * Similarly, Allocator of default device was used with test-specific
device objects.

 * Several objects were leaked.

Bug: 28074219
Change-Id: I7588ce3eac07919e958f722168f2d83401e7e038