Allow multiple preemptible instances to be created

[jbaublitz]

Allow multiple preemptible instances to be created with ex_create_multiple_nodes

Description

This change enables multiple nodes to be created as preemptible on Google Cloud through the ex_create_multiple_nodes function call. Currently, this parameter is supported in the underlying functions in libcloud called by ex_create_multiple_nodes such as _create_node_req but the function itself does not expose this parameter at the top level. This patch enables a cluster of preemptible instances to be provisioned in parallel.

Status

• ready for review

Checklist (tick everything that applies)

• Code linting (required, can be done after the PR checks)
• Documentation
• Tests
• ICLA (required for bigger changes)

\cc @supertom @erjohnso

[jbaublitz]

@supertom This pull request is important for ansible now that ansible's gce module uses ex_create_multiple_nodes and provides the same parameters conditionally to both create_node and ex_create_multiple_nodes based on the number parameter. I recently tried to provision a cluster of preemptible nodes from ansible and libcloud notified me that ex_preemptible was not a supported parameter. I have tested the custom build of libcloud with this patch and it fixes the behavior I described in ansible in that use case.

[supertom]

Thanks @jbaublitz! LGTM! @erjohnso, OK to merge.

[jbaublitz]

Just for the sake of a breadcrumb trail, I'm going to link to the PR in ansible which will depend on the release including this PR to properly execute. ansible/ansible-modules-core#4276

[jbaublitz]

@supertom @erjohnso Is there a status on merge date?

[tonybaloney]

sorry @jbaublitz this got left a bit too long. merging.