[MemSheriff] Suppress broken test.

BUG=394460
TBR=thestig@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/395253003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@283577 0039d316-1c4b-4281-b951-d872f2087c98

tools/valgrind/gtest_exclude/unit_tests.gtest-drmemory.txt

+# Flaky, see http://crbug.com/394460
+SyncFileSystemServiceTest.SimpleLocalSyncFlow

tools/valgrind/gtest_exclude/unit_tests.gtest-memcheck_linux.txt

+# Flaky, see http://crbug.com/394460
+SyncFileSystemServiceTest.SimpleLocalSyncFlow