iteritems() was dropped in recent Python3 releases and items() is compatible
with Python 2.7.

- Add posibility do delete user password
 - Delete any password, if no other option has been passed
 - Allow to pass hash\plain password
 - Allow to unchange password

Change-Id: Id2b7234ca5d4417475b2114e74840292fc57d0de

Change-Id: I2163dbdee38e1b9c5c4dec6611550f16fdf1373b

Change-Id: I9767e07ffe3a808ee9a2de925862ba193b7b612e

Remove sudo files for users, which still exists, but don't have enabled sudo.

- apply review comments
- add visudo check cmd