selftests: futex Makefile add top level TAP header echo to RUN_TESTS

Add top level TAP header echo, testname and separator line to make
the output consistent with the common run_tests target.

This change prevents nested TAP13 headers output from individual tests.
Nested TAP13 headers could cause problems for some parsers.

Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>
Reviewed-by: Darren Hart (VMware) <dvhart@infradead.org>
Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>