Show message when trying to edit item with missing Provisioning request

[h-kataria]

Added check around code to prevent error when editing catalog item with missing Provisioning request, with this change, flash message will be displayed on the screen informing user that they can not proceed with editing selected catalog item because request is missing

Fixes https://bugzilla.redhat.com/show_bug.cgi?id=1476949
@lgalis please review/test, to test this, you will need to delete a provisioning request associated with a catalog item manually from your database.
@dclarizio please review

[miq-bot]

Checked commit h-kataria@6a24e66 with ruby 2.3.3, rubocop 0.52.1, haml-lint 0.20.0, and yamllint 1.10.0
3 files checked, 1 offense detected

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• 💣 💥 🔥 🚒 - Linter/Haml - Linter::Haml STDERR:

warning: parser/current is loading parser/ruby23, which recognizes
warning: 2.3.6-compliant syntax, but you are running 2.3.3.
warning: please see https://github.com/whitequark/parser#compatibility-with-ruby-mri.

[simaishi]

@h-kataria Can this be fine/yes ?

[h-kataria]

@simaishi looks like it should be ok to backport this to Fine.

[simaishi]

Gaprindashvili backport details:

$ git log -1
commit f1a1dfa8bdcb0768a2ad414ea1a19546250b3107
Author: Dan Clarizio <[email protected]>
Date:   Tue Mar 20 15:32:19 2018 -0700

    Merge pull request #3661 from h-kataria/catalog_item_missing_request_fix
    
    Show message when trying to edit item with missing Provisioning request
    (cherry picked from commit 09b7417c99f087c528caae02abb909186868e14d)
    
    Fixes https://bugzilla.redhat.com/show_bug.cgi?id=1560096

[simaishi]

@h-kataria There are conflicts backporting to Fine branch. Please create a separate PR.

[simaishi]

Backported to Fine via #3746