Currently both neutron-server and separate service packages are
installed regardless of the services actually used. However this is
quite redundant especially when only neutron-server is used in CentOS.
Skip installation of separate packages when the monolithic server
service is requested.
Change-Id: I72359a2e78c57de57722d01b4c16c0db85189f54
(cherry picked from commit a4d9425fe859c4a6ab322c5985f294368d6149c6)