ci: do not run tests requiring iptables if it is missing

There are a couple of tests that require the iptables binary.

Instead of adding a checkskip script, which could also handle this,
this change now uses CRIU's feature detection to see if the CRIU
feature 'has_ipt_legacy' exists.

Signed-off-by: Adrian Reber <areber@redhat.com>

test/zdtm/static/net_lock_socket_iptables.desc

@@ -1,5 +1,6 @@
 {
     'flavor': 'h',
+    'feature': 'has_ipt_legacy',
     'flags': 'suid excl reqrst',
     'dopts': '--tcp-established --network-lock iptables',
     'ropts': '--tcp-established',

test/zdtm/static/net_lock_socket_iptables6.desc

@@ -1,5 +1,6 @@
 {
     'flavor': 'h',
+    'feature': 'has_ipt_legacy',
     'flags': 'suid excl reqrst',
     'dopts': '--tcp-established --network-lock iptables',
     'ropts': '--tcp-established',

test/zdtm/static/netns-nf.desc

@@ -3,4 +3,5 @@
                 '/lib/xtables/libxt_standard.so|/usr/lib64/xtables/libxt_standard.so|/usr/lib/iptables/libxt_standard.so|/usr/lib/powerpc64le-linux-gnu/xtables/libxt_standard.so|/usr/lib/x86_64-linux-gnu/xtables/libxt_standard.so|/usr/lib/s390x-linux-gnu/xtables/libxt_standard.so|/usr/lib/xtables/libxt_standard.so|/usr/lib/aarch64-linux-gnu/xtables/libxt_standard.so|/usr/lib/riscv64-linux-gnu/xtables/libxt_standard.so',
                 '/usr/bin/diff'],
     'flags': 'suid',
+    'feature': 'has_ipt_legacy',
     'flavor': 'ns uns'}

test/zdtm/static/netns_lock_iptables.desc

@@ -1,6 +1,7 @@
 {
     'flavor': 'h',
     'flags': 'suid excl reqrst',
+    'feature': 'has_ipt_legacy',
     'opts': '--tcp-established',
     'dopts': '--network-lock iptables',
     'ropts': '--join-ns net:/var/run/netns/criu-net-lock-test'

test/zdtm/static/socket-tcp-closed-last-ack.desc

@@ -5,6 +5,6 @@
 	],
 	'opts': '--tcp-established',
 	'flags': 'suid nouser samens',
-	'feature' : 'tcp_half_closed',
+	'feature' : 'tcp_half_closed has_ipt_legacy',
 	'flavor': 'ns uns',
 }

test/zdtm/static/socket-tcp-reseted.desc

@@ -6,5 +6,5 @@
        ],
        'opts': '--tcp-established',
        'flags': 'suid nouser samens',
-       'feature' : 'tcp_half_closed'
+       'feature' : 'tcp_half_closed has_ipt_legacy'
 }

test/zdtm/static/socket-tcp-syn-sent.desc

@@ -5,5 +5,5 @@
 	],
 	'opts': '--tcp-established',
 	'flags': 'suid nouser samens',
-	'feature' : 'tcp_half_closed'
+	'feature' : 'tcp_half_closed has_ipt_legacy'
 }