(#19542) useradd provider should support move-home option if managehome is enabled

usermod has a flag (-m) to move a users home directory when it's being modified, this
adds modifycmd to the useradd provider which will run usermod with the -m option.
(#18229) - Eroneous command given in puppet module error message

Fixed the error message to read --target-dir instead of --dir
Merge pull request #1513 from casharma/bugfix/module/18229

(#18229) - Eroneous command given in puppet module error message
(#19542) Update user type docs for linux managehome

Commit d23906e adds support for updating the user home directory if the
`managehome` parameter is true. This commit updates the user type
documentation to note the Linux exception since the behavior change is
only applicable to Linux.
Merge branch 'pull-1512'