Add containers-common spec and command to podman

Since containers-common package is tied to specific versions
of Podman, add tools to build the package into the contrib directory
This should help other distributions to figure out which commont
package to ship.

Signed-off-by: Daniel J Walsh <dwalsh@redhat.com>

vendor/github.com/prometheus/procfs/proc_cgroup.go

@@ -90,7 +90,7 @@ func parseCgroups(data []byte) ([]Cgroup, error) {
 // control hierarchy running on this system. On every system (v1 and v2), all hierarchies contain all processes,
 // so the len of the returned struct is equal to the number of active hierarchies on this system
 func (p Proc) Cgroups() ([]Cgroup, error) {
-	data, err := util.ReadFileNoStat(fmt.Sprintf("/proc/%d/cgroup", p.PID))
+	data, err := util.ReadFileNoStat(p.path("cgroup"))
 	if err != nil {
 		return nil, err
 	}