Use the groups defined in swift_services to determine which distro
packages to install onto hosts instead of installing all distro service
packages on all swift hosts.
The 'swift-plugin-s3' package has also been removed from debian's
package list. s3api should be configured through swift middleware instead.
Change-Id: I1e7a8eba6500c819d418ee565a5f03cc16dfe165
3d9567ebad