Rename Admin User Guide PDF
Rename Admin User Guide PDF

Remove the -trunk from the file name, it's not needed anymore, this was
the only PDF file having -trunk in the name.

Also, use user-guide-admin to follow the naming of directory and web
page.

Change-Id: I3e3ef6bfa23ed35fb81c568955df67aee27e5104

AlekhyaMallina-Vedams/openstack-manuals,openstack/openstack-manuals,AlekhyaMallina-Vedams/openstack-manuals,saeki-masaki/openstack-manuals,openstack/openstack-manuals,Akasurde/openstack-manuals,openstack/openstack-manuals,kairoaraujo/openstack-manuals,kairoaraujo/openstack-manuals,openstack/openstack-manuals,gongysh2004/openstack-manual,Akasurde/openstack-manuals,potsmaster/openstack-manuals,saeki-masaki/openstack-manuals,AlekhyaMallina-Vedams/openstack-manuals,potsmaster/openstack-manuals,gongysh2004/openstack-manual