Fix LoggerTest.

Two of the tests in this class currently fail because assertSame() is
used on Strings that are equal but not the same object. That's probably
unintentional and changing those instances to assertEquals() fixes the
test.

Test: run cts -m CtsLibcoreTestCases -t com.android.org.apache.harmony.logging.tests.java.util.logging.LoggerTes
Change-Id: I89226e43fce16e3ebdbede446b7ce2c527a096ed