Fix docstring indentation in systemd

This gives overwise an error when building Sphinx documentation:

docstring of keystone.openstack.common.systemd.notify:3: ERROR:
Unexpected indentation.

Fix another small docstring formatting error alongway.

Change-Id: I403dacfcb65c1dbffc12edf102a36b3177eb944c
Merge "Fix docstring indentation in systemd"