test: Add debian dependency at netns-nf.desc

Make Debian great again!

Travis: https://travis-ci.org/criupatchwork/criu/builds/171342703Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>

test/zdtm/static/netns-nf.desc

-{'flavor': 'ns uns', '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/bin/diff' ], 'flags': 'suid'}
+{'flavor': 'ns uns', '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/bin/diff' ], 'flags': 'suid'}