Write rd_CCW when root fs is on a network device on s390x (#577193)

The dracutSetupString() method in the Network class needed to write out
the rd_CCW parameter, which is necessary for network devices on s390x.
The format is described in the dracut(8) man page.  The required
information has always been written to the ifcfg-DEVICE file, so we just
need to make sure it gets to dracut as well.

network.py

@@ -823,4 +823,17 @@ def dracutSetupString(self, networkStorageDevice):
 
  netargs += "ifname=%s:%s" % (nic, hwaddr.lower())
 
+ nettype = dev.get("NETTYPE")
+ subchannels = dev.get("SUBCHANNELS")
+ if iutil.isS390() and nettype and subchannels:
+ if netargs != "":
+ netargs += " "
+
+ netargs += "rd_CCW=%s,%s" % (nettype, subchannels)
+
+ options = dev.get("OPTIONS")
+ if options:
+ options = filter(lambda x: x != '', options.split(' '))
+ netargs += ",%s" % (','.join(options))
+
  return netargs