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)" <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>