test: disable ex_libpmem2/TEST6 for 'helgrind' until pmem#5638 is fixed

Disable ex_libpmem2/TEST6 for 'helgrind'
until the issue pmem#5638 is fixed.

Signed-off-by: Tomasz Gromadzki <tomasz.gromadzki@intel.com>

src/test/ex_libpmem2/TESTS.py

@@ -100,9 +100,9 @@ class TEST501(EX_LIBPMEM2_TEST5):  # to be removed when fixed
 
 
 @t.windows_exclude
-# XXX disable the test for `memcheck'
+# XXX disable the test for `memcheck' and 'helgrind'
 # until https://github.com/pmem/pmdk/issues/5638 is fixed.
-# @t.require_valgrind_disabled('memcheck')
+# @t.require_valgrind_disabled('memcheck', 'helgrind')
 # XXX disable the test for `drd'
 # until https://github.com/pmem/pmdk/issues/5593 is fixed.
 # @t.require_valgrind_disabled('drd')
@@ -114,7 +114,7 @@ class TEST501(EX_LIBPMEM2_TEST5):  # to be removed when fixed
 # complication), so this test case just should not be run under pmemcheck.
 # @t.require_valgrind_disabled('pmemcheck')
 # XXX _disabled() can be used only once.
-@t.require_valgrind_disabled('memcheck', 'drd', 'pmemcheck')
+@t.require_valgrind_disabled('memcheck', 'drd', 'pmemcheck', 'helgrind')
 class TEST6(EX_LIBPMEM2):
 
     def run(self, ctx):