Remove the -only CLI option for packer build

Remove the -only CLI option for packer build

The #CR 90dd675df482a8 submitted with common-packer v0.7.0
fails to build packer jobs because of a bug in the packer build CLI.

The `-only` option packer build CLI does not set the cloud provider
name/type as per the documentation. The alternative is to use an environment
variable that is passed through the packer job and can be reference in the
packer templates.

Issue: JIRA IT-21300
Github Issue: https://github.com/hashicorp/packer/issues/10495
Ref: https://gerrit.linuxfoundation.org/infra/c/releng/common-packer/+/66528
Change-Id: I97bc479ddac9a8f1f0dc83201735b0a084a8b3e4
Signed-off-by: Anil Belur <abelur@linuxfoundation.org>