Update CSE guide with some hints and improvements in the process

[adambarreiro]

Description

This PR complements #856 and #876 with extra hints and steps that were not taken into account in the mentioned changes.

• Mentions TKGm version used in downloaded OVAs in the example, to let customers to have more context where the OVA comes from.
• Onboards the service account role mentioned in CSE documentation to be used instead of system administrator for CSE installation.

PS: The list of rights for the role is taken from here.

Tests

• Example HCL finishes correctly in VCD 10.3.2
• Cluster successfully created
• Tested with CSE 3.1.4

[adambarreiro]

I've updated also the Guide with this alias approach, to have more consistency between the example HCL code and the Guide.

[vmwclabot]

@adambarreiro, you must sign every commit in this pull request acknowledging our Developer Certificate of Origin before your changes are merged. This can be done by adding Signed-off-by: John Doe <john.doe@email.org> to the last line of each Git commit message. The e-mail address used to sign must match the e-mail address of the Git author. Click here to view the Developer Certificate of Origin agreement.

• Commit a0a5b0a must be signed by abarreiro@vmware.com

[vmwclabot]

@adambarreiro, you must sign every commit in this pull request acknowledging our Developer Certificate of Origin before your changes are merged. This can be done by adding Signed-off-by: John Doe <john.doe@email.org> to the last line of each Git commit message. The e-mail address used to sign must match the e-mail address of the Git author. Click here to view the Developer Certificate of Origin agreement.

• Commit a0a5b0a must be signed by abarreiro@vmware.com

[adambarreiro]

Improved null_resource.cse-install-script as doing a terraform plan without any change in infrastructure was showing changes, as the resource was forced to always re-create. Now it's only re-creating when a required field is changed.

[Didainius]

Thanks!

[vmwclabot]

@adambarreiro, you must sign every commit in this pull request acknowledging our Developer Certificate of Origin before your changes are merged. This can be done by adding Signed-off-by: John Doe <john.doe@email.org> to the last line of each Git commit message. The e-mail address used to sign must match the e-mail address of the Git author. Click here to view the Developer Certificate of Origin agreement.

• Commit aa1b037 must be signed by abarreiro@vmware.com

[vmwclabot]

@adambarreiro, you must sign every commit in this pull request acknowledging our Developer Certificate of Origin before your changes are merged. This can be done by adding Signed-off-by: John Doe <john.doe@email.org> to the last line of each Git commit message. The e-mail address used to sign must match the e-mail address of the Git author. Click here to view the Developer Certificate of Origin agreement.

• Commit aa1b037 must be signed by abarreiro@vmware.com