Log an ignore non-fatal errors in deleteRuntimeArtifacts.

This is to comform with the javadoc on this method, which says "Throws
fatal errors. Logs and ignores non-fatal errors." Also, the binder
caller does not expect non-fatal errors and does not handle them.

Test: m test-art-host-gtest-art_artd_tests
Change-Id: If8419e7c3439be35719a09bd14e83342ae4c2442