* Allow an admin to define the "uid" attribute for a RFC2307

* Allow an admin to define the "uid" attribute for a RFC2307
  user object in AD to be the username alias.

For example:

  $ net ads search "(uid=coffeedude)"
  distinguishedName: CN=Gerald W. Carter,CN=Users,DC=pink,DC=plainjoe,DC=org
  sAMAccountName: gcarter
  memberOf: CN=UnixUsers,CN=Users,DC=pink,DC=plainjoe,DC=org
  memberOf: CN=Domain Admins,CN=Users,DC=pink,DC=plainjoe,DC=org
  memberOf: CN=Enterprise Admins,CN=Users,DC=pink,DC=plainjoe,DC=org
  memberOf: CN=Schema Admins,CN=Users,DC=pink,DC=plainjoe,DC=org
  uid: coffeedude
  uidNumber: 10000
  gidNumber: 10000
  unixHomeDirectory: /home/gcarter
  loginShell: /bin/bash

  $ ssh coffeedude@192.168.56.91
  Password:

  coffeedude@orville:~$ id
  uid=10000(coffeedude) gid=10000(PINK\unixusers) groups=10000(PINK\unixusers)

  $ getent passwd PINK\\gcarter
  coffeedude:*:10000:10000::/home/gcarter:/bin/bash

  $ getent passwd coffeedude
  coffeedude:*:10000:10000::/home/gcarter:/bin/bash

  $ getent group PINK\\Unixusers
  PINK\unixusers:x:10000:coffeedude
(cherry picked from commit 7cdcf4dff2cb02ec16f4e78b85701cd2043be274)