in netinfo output (ci-info:), fill in empty fields with a "."

If you were trying to parse this output with something, an empty field would be
difficult to handle, as you'd have to know the expected lengths of each field.
The '.' means empty, but then all fields are non-whitespace delimited by one or
more whitespace.

ChangeLog

@@ -20,6 +20,7 @@
  - add test case framework [Mike Milner] (LP: #890851)
  - fix pylint warnings [Juerg Haefliger] (LP: #914739)
  - add support for adding and deleting CA Certificates [Mike Milner] (LP: #915232)
+ - in ci-info lines, use '.' to indicate empty field for easier machine reading
 0.6.2:
  - fix bug where update was not done unless update was explicitly set.
    It would not be run if 'upgrade' or packages were set to be installed

cloudinit/netinfo.py

@@ -22,7 +22,7 @@
 import subprocess
 
 
-def netdev_info():
+def netdev_info(empty=""):
     fields = ("hwaddr", "addr", "bcast", "mask")
     ifcfg_out = str(subprocess.check_output(["ifconfig", "-a"]))
     devs = {}
@@ -59,6 +59,13 @@ def netdev_info():
                         pass
                 elif toks[i].startswith("%s:" % field):
                     devs[curdev][target] = toks[i][len(field) + 1:]
+
+    if empty != "":
+        for (devname, dev) in devs.iteritems():
+            for field in dev:
+                if dev[field] == "":
+                    dev[field] = empty
+
     return(devs)
 
 
@@ -85,7 +92,7 @@ def getgateway():
 def debug_info(pre="ci-info: "):
     lines = []
     try:
-        netdev = netdev_info()
+        netdev = netdev_info(empty=".")
     except Exception:
         lines.append("netdev_info failed!")
         netdev = {}