Description of problem:

Previously loaded and selected VPC shown as default value for "Specify a VPC to install your machine pools into" for a fresh ROSA Hypershift wizard.

This needs to be changed and expected behavior as below. 

1. The "Specify a VPC to install your machine pools into" value should be "Select VPC" as it is a fresh ROSA flow and user need to make a choice.
2. The machine pool entry with validation error shouldn't be shown instead user should have an option "Add machine pool" with no existing machine pool entry.

How reproducible:

 Always

Steps to reproduce:

1. Launch OCM Staging.
2. Open ROSA wizard and select control plane type as "Hosted"
3. Proceed to next steps by providing all required values in each step.
4. Reach to "Machine pool" step .
5. Select a VPC from  "Specify a VPC to install your machine pools into" list.
6. Click on "Add machine pool" and select a private subnet id for the same.
7. Click on "next" button.
8. Click on "cancel" button and leave the wizard.
9. Repeat the step 2 to 4 and see the behavior.

Actual results:

On a fresh ROSA hypershift wizard, the previously selected VPC with a empty private subnet ID field contains a validation error shown on the machine pool step. This is wrong.

Expected results:
On a fresh ROSA hypershift wizards,

1. The "Specify a VPC to install your machine pools into" value should be "Select VPC" as it is a fresh ROSA flow and user need to make a choice.
2. The machine pool entry with validation error shouldn't be shown instead user should have an option "Add machine pool" with no existing machine pool entry.

Refer attached screen recordings VPCExistingValues.mp4