Revert "Do not enumerate ipv6 routes in CentOS 4"

This reverts commit 5186c408f7.

system/setup

@@ -1370,10 +1370,6 @@ class LinuxNetwork(Network):
         )
         interface = dict(v4 = {}, v6 = {})
         for v in 'v4', 'v6':
-            if v == 'v6' and self.facts['lsb']['id'] == 'CentOS' \
-                and self.facts['lsb']['major_release'] == '4':
-                # "ip -6 route get" causes kernel panics in Centos 4
-                continue
             if v == 'v6' and not socket.has_ipv6:
                 continue
             rc, out, err = module.run_command(command[v])