[6.14.z] Fix upload_manifest to handle case where manifest.content is not set

[Satellite-QE]

Cherrypick of PR: #13819

Problem Statement

Currently, there are many intermittent test failures like below where we use module_sca_manifest_org are seen in automation runs, where we don't have content property set in manifester object.

pytest_fixtures/component/taxonomy.py:102: in module_sca_manifest_org
    module_target_sat.upload_manifest(module_org.id, module_sca_manifest.content)
robottelo/host_helpers/satellite_mixins.py:149: in upload_manifest
    if manifest.content is None:
E   AttributeError: 'NoneType' object has no attribute 'content'

Solution

Update upload_manifest to handle case where manifest.content is not set, or when manifest.content is None

Local test results:

In [3]: manifest = Manifester(manifest_category=settings.manifest.golden_ticket)

In [4]: manifest.content
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
Cell In[4], line 1
----> 1 manifest.content

AttributeError: 'Manifester' object has no attribute 'content'

In [5]: hasattr(manifest, 'content')
Out[5]: False

In [6]: not hasattr(manifest, 'content') or manifest.content is None
Out[6]: True

In [7]: manifest.content = None

In [8]: not hasattr(manifest, 'content') or manifest.content is None
Out[8]: True

[Satellite-QE]

trigger: test-robottelo
pytest: tests/foreman/cli/test_activationkey.py tests/foreman/api/test_subscription.py tests/foreman/cli/test_contentaccess.py -k 'test_positive_add_redhat_product or test_negative_upload or test_negative_rct_not_shows_golden_ticket_enabled'