Add integration tests node-specific configuration

[engelmi]

In #1023 we added the feature to configure specific options for nodes in the bluechi-controller such as a required SELinux context the connecting agent should be running in. Now we need to add integration tests to ensure this works as expected.

For this we should add the following tests:

• Verify the node-specific Allowed option enables/disables the agent to connect
• Verify the node-specific RequiredSelinuxContext option works as expected
  Note:
  These RequiredSelinuxContext test cases require SELinux and thus will not work in the GH CI (using Ubuntu VMs). Therefore, these tests need to be tagged with testing-farm-container in order to run them only on Testing Farm.

[alexlarsson]

The allowed case should work fine anywhere, but the selinux one, no.