deploy-test: pre-install requests

These tests are still using python setup.py test which installs missing packages to their latest versions. Recently, certifi (a requests dependency) published a new release with python3 only syntax, so running the test now got an error installing missing packages:

File "parts/slapos-package/playbook/roles/standalone-shared/.eggs/certifi-2022.5.18.1-py2.7.egg/certifi/core.py", line 17
    def where() -> str:
                ^
SyntaxError: invalid syntax

The playbook/roles/standalone-shared is defined on the test suite as instance parameters, so it seems we can not already install this package directly from playbook/roles/standalone-shared because test suite may define something different. For now, just install requests. All this will have to be addressed when we change this test to pre-install packages with slapos and use python -m unittest instead of python setup.py test.