avoid ZeroDevisionError exception when swap memory is 0

[yulin-li]

Description

got ZeroDevisionError

Callback failed for instrument system.swap.utilization.
Traceback (most recent call last):
  File "/usr/local/lib/python3.8/dist-packages/opentelemetry/sdk/metrics/_internal/instrument.py", line 132, in callback
    for api_measurement in callback(callback_options):
  File "/usr/local/lib/python3.8/dist-packages/opentelemetry/instrumentation/system_metrics/__init__.py", line 515, in _get_system_swap_utilization
    getattr(system_swap, metric) / system_swap.total,
ZeroDivisionError: division by zero

Fixes #1337

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• Test A

Does This PR Require a Core Repo Change?

• Yes. - Link to PR:
• No.

Checklist:

See contributing.md for styleguide, changelog guidelines, and more.

• Followed the style guidelines of this project
• Changelogs have been updated
• Unit tests have been added
• Documentation has been updated

[yulin-li]

could we get this merged? @lzchen

[lzchen]

@yulin-li
Please fix build issues.

[yulin-li]

@yulin-li Please fix build issues.

I believe I fixed the lint issue and verified using python scripts/eachdist.py lint locally.