autohelp: import oslo extensions only if needed
autohelp: import oslo extensions only if needed

Oslo modules are not used by all the components, so configuration
options might be invalid if these modules are unconditionaly loaded.
This change uses the requirements.txt file of a project to detect if
oslo modules have to be imported.

Change-Id: I7cd81d0c9a5ae43f0a628e2d2a6f664507e54122

openstack/openstack-doc-tools,savinash47/openstack-doc-tools,savinash47/openstack-doc-tools,savinash47/openstack-doc-tools,openstack/openstack-doc-tools