Node Management: Salt Precheck before creating a node

[carlito-scality]

Component:Salt

Why this is needed:

• It would be helpful if we can precheck the node configuration in the node creation form of the UI before the creation to try to avoid error when deploying.

What should be done:

• A precheck in the salt API
• In the node creation form of the UI, rename "Create" to "Check and Create" ?! and call this above precheck before submitting creation request

Implementation proposal (strongly recommended):

Test plan:

[thomasdanan]

relates to #3392