Plans Update : adding disk_count

[ddymko]

Description

The field disk_count was added to all plans for instances and baremetal. This denotes how many disks are available with the plan

Related Issues

Checklist:

• Have you checked to ensure there aren't other open Pull Requests for the same update/change?
• Have you linted your code locally prior to submission?
• Have you successfully ran tests with your changes locally?

[codecov]

Codecov Report

Merging #130 (c0512f7) into master (84c673b) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #130   +/-   ##
=======================================
  Coverage   55.00%   55.00%           
=======================================
  Files          23       23           
  Lines        1169     1169           
=======================================
  Hits          643      643           
  Misses        264      264           
  Partials      262      262           

Impacted Files	Coverage Δ
plans.go	53.84% <ø> (ø)

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