mate-screenshot do not allow to set delay when taking screenshot of area interactively

[Norbert]

Steps to reproduce:
1. Install `ubuntu-mate-desktop` on Ubuntu 17.10 or 18.04 LTS
2. Try to make screenshot of area with <Shift+PrintScreen> or by `mate-screenshot -a -i`
3. Try to set delay in opened window

Expected results:
User is able to set delay when taking screenshot of area with <Shift+PrintScreen>.

Actual results:
User is unable to set delay when taking screenshot of area with <Shift+PrintScreen>.

Note: this works as expected on 16.04 LTS - user is able to set delay and area when taking screenshot of area with <Shift+PrintScreen>.

First seen on AskUbuntu (https://askubuntu.com/q/1008771/66509).

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: mate-utils 1.20.0-0ubuntu1
ProcVersionSignature: Ubuntu 4.13.0-32.35-generic 4.13.13
Uname: Linux 4.13.0-32-generic x86_64
ApportVersion: 2.20.8-0ubuntu10
Architecture: amd64
CurrentDesktop: MATE
Date: Fri Feb 23 00:04:09 2018
InstallationDate: Installed on 2017-12-22 (62 days ago)
InstallationMedia: Ubuntu 18.04 LTS "Bionic Beaver" - Alpha amd64 (20171221)
SourcePackage: mate-utils
UpgradeStatus: No upgrade log present (probably fresh install)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.