netfilter: selftest: conntrack_vrf.sh: fix file permission

When backporting 33b8aad ("selftests: netfilter: add a
vrf+conntrack testcase") to this stable branch, the executable bits were
not properly set on the
tools/testing/selftests/netfilter/conntrack_vrf.sh file due to quilt not
honoring them.

Fix this up manually by setting the correct mode.

Reported-by: "Rantala, Tommi T. (Nokia - FI/Espoo)" <tommi.t.rantala@nokia.com>
Link: https://lore.kernel.org/r/234d7a6a81664610fdf21ac72730f8bd10d3f46f.camel@nokia.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>