ltp: make syncfs01 optional

Older kernels have a problem with /sys/block/<device>/stat which
prevents this test from running (it instead returns TCONF). Make the
test optional to account for this.

Bug: 139101484
Change-Id: Iae9c21457d4419f27944125ef245bfb3c13c3363
diff --git a/ltp/configs/stable_tests.py b/ltp/configs/stable_tests.py
index a96153d..ba160f8 100644
--- a/ltp/configs/stable_tests.py
+++ b/ltp/configs/stable_tests.py
@@ -2076,8 +2076,8 @@
     ('syscalls.sync02_64bit', True),
     ('syscalls.sync_file_range01_32bit', True),
     ('syscalls.sync_file_range01_64bit', True),
-    ('syscalls.syncfs01_32bit', True),
-    ('syscalls.syncfs01_64bit', True),
+    ('syscalls.syncfs01_32bit', False),
+    ('syscalls.syncfs01_64bit', False),
     ('syscalls.syscall01_32bit', False),
     ('syscalls.syscall01_64bit', False),
     ('syscalls.sysconf01_32bit', False),