Update the xtables deps for netns-test.

In some distros (such as Arch), libxtables_standard is part of iptables
as `/usr/lib/iptables/libxt_standard.so`. With this change, the test passes,
otherwise netns-nf test fails.

Tested with make test.
Signed-off-by: Raghavendra D Prabhu <me@rdprabhu.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>

test/zdtm/static/netns-nf.desc

 {   'deps': [   '/bin/sh',
                 '/sbin/iptables',
-                '/usr/lib64/xtables/libxt_standard.so|/lib/xtables/libxt_standard.so|/usr/lib/powerpc64le-linux-gnu/xtables/libxt_standard.so|/usr/lib/x86_64-linux-gnu/xtables/libxt_standard.so',
+                '/usr/lib64/xtables/libxt_standard.so|/usr/lib/iptables/libxt_standard.so|/lib/xtables/libxt_standard.so|/usr/lib/powerpc64le-linux-gnu/xtables/libxt_standard.so|/usr/lib/x86_64-linux-gnu/xtables/libxt_standard.so',
                 '/usr/bin/diff'],
     'flags': 'suid',
     'flavor': 'ns uns'}