Disable SELinux for libcompositionengine_test

SELinux prevents stack traces from being reachable, and these tests
don't try to exercise SELinux anyways.

Bug: 307776985
Test: Trigger a crash libcompositionengine_test and see if a
symbolizable stack is tombstoned

Change-Id: I1f3789c52123776d843ff0b55b310d8795597819