test/zdtm: fix netns-nf dependency on ppc64

On Ubuntu ppc64le, the libxt_standard.so is installed under a
different path.
Adding this path to the dependency list to make the test running on
ppc64le.
Signed-off-by: Laurent Dufour <ldufour@linux.vnet.ibm.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/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/bin/diff' ], 'flags': 'suid'}