Add skip_build_key_vault_create to skip build Keyvault create during window builds

[garimakhulbe02]

This PR is add this attribute #357

New attribute/input skip_build_key_vault_create in packer config to skip Keyvault deployment during packer build for windows images. Packer does two ARM deployments during build. First deployment for Keyvault to save WinRM certificate and second deployment for build VM. This attribute will give an option to skip this build Keyvault deployment during build.