Subscription ID is required when adding, readOnly when editing (Azure)

[rvsia]

Fixes https://bugzilla.redhat.com/show_bug.cgi?id=1519359

Description

Compute > Clouds > Providers > Edit selected (Azure) / Add a new Cloud Provider

Expected results
Subscription ID should be

• required field when adding an Azure Provider
• a read only field when edititng existing Azure provider.

Before

After

[miq-bot]

Checked commit rvsia@95df1ce with ruby 2.3.3, rubocop 0.52.1, haml-lint 0.20.0, and yamllint 1.10.0
1 file checked, 1 offense detected

**

• 💣 💥 🔥 🚒 - 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.

[rvsia]

@miq-bot add_label hammer/yes, compute/cloud, bug