Make testMediaserverDomain() pass

When ro.test_harness=1, mediaserver forks and creates a new process
called "media.log". This confuses the CTS test, which thinks
there's an invalid process running under the mediaserver SELinux
domain.

Fix testMediaserverDomain() so it understands media.log.

Change-Id: I34072e2d85ba63336d6d9d7dce697ed1143056cd