fix adding of users when no group is specified

revision 1179 regressed adding a user that did not have a 'groups'
entry present in cloud-config.
This handles that correctly, making 'add_user' able to take:
  a.) groups="group1,group2"
  b.) groups=["group1", "group2"]
  c.) groups=None
  d.) no groups parameter

Additionally, if a primary group is specified it will also be created.

End result is that this is functional:
 #cloud-config
 groups: ["sudo"]
 users:
   - name: sysop
     primary-group: sysop
     groups: "sudo,adm"
     shell: /bin/bash
   - name: user1
     primary-group: users
     groups: sudo
   - name: foo1
   - name: bar
     gecos: Bar
     groups: ["bargroup"]

Resulting in:
 $ groups sysop
 sysop : sysop adm sudo
 $ groups user1
 user1 : users sudo
 $ groups foo1
 foo1 : foo1
 $ groups bar
 bar : bar bargroup

LP: #1562918

1 files changed, 9 insertions, 2 deletions

diff --git a/cloudinit/distros/__init__.py b/cloudinit/distros/__init__.py
index 12983c0a..5879dabf 100644
--- a/cloudinit/distros/__init__.py
+++ b/cloudinit/distros/__init__.py
@@ -362,15 +362,22 @@ class Distro(object):
 
         redact_opts = ['passwd']
 
+        # support kwargs having groups=[list] or groups="g1,g2"
         groups = kwargs.get('groups')
         if groups:
             if isinstance(groups, (list, tuple)):
+                # kwargs.items loop below wants a comma delimeted string
+                # that can go right through to the command.
                 kwargs['groups'] = ",".join(groups)
             else:
                 groups = groups.split(",")
 
-        if create_groups:
-            for group in kwargs.get('groups').split(","):
+            primary_group = kwargs.get('primary_group')
+            if primary_group:
+                groups.append(primary_group)
+
+        if create_groups and groups:
+            for group in groups:
                 if not util.is_group(group):
                     self.create_group(group)
                     LOG.debug("created group %s for user %s", name, group)