Improve error handling in AD/LDAP sync process.

[brian-emery]

There are numerous situations in which the AD/LDAP sync can fail on a specific user. However, it would be better if we could continue to sync the rest of the users and log/display the users who were not able to be synced. I'll be using this issue to track situations that cause the sync to fail.

[brian-emery]

If a local user is added to the OMVA, then a user with the same email/username is added via AD/LDAP, the sync will fail:

Unable to create {'group_id': 139, 'plan_id': 32688, 'email': 'user1005@newben.com', 'name': 'user1005'}. Got error during runall, aborted on action: create

and any additional users will not be synced.

[merickson]

In the case of the above comment, see #196 . That does not invalidate the point of this issue, however.