selftests: net: check jq command is supported

The jq command is used in vlan_bridge_binding.sh, if it is not supported,
the test will spam the following log.

  # ./vlan_bridge_binding.sh: line 51: jq: command not found
  # ./vlan_bridge_binding.sh: line 51: jq: command not found
  # ./vlan_bridge_binding.sh: line 51: jq: command not found
  # ./vlan_bridge_binding.sh: line 51: jq: command not found
  # ./vlan_bridge_binding.sh: line 51: jq: command not found
  # TEST: Test bridge_binding on->off when lower down                   [FAIL]
  #       Got operstate of , expected 0

The rtnetlink.sh has the same problem. It makes sense to check if jq is
installed before running these tests. After this patch, the
vlan_bridge_binding.sh skipped if jq is not supported:

  # timeout set to 3600
  # selftests: net: vlan_bridge_binding.sh
  # TEST: jq not installed                                              [SKIP]

Fixes: dca12e9a ("selftests: net: Add a VLAN bridge binding selftest")
Fixes: 6a414fd7 ("selftests: rtnetlink: Add an address proto test")
Signed-off-by: Wang Liang <wangliang74@huawei.com>
Reviewed-by: Hangbin Liu <liuhangbin@gmail.com>
Link: https://patch.msgid.link/20251013080039.3035898-1-wangliang74@huawei.com


Signed-off-by: Paolo Abeni <pabeni@redhat.com>