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

0 files changed, 0 insertions, 0 deletions