Support pods with containers using host ipc

Add a HostIPC field to the Pod Spec to create containers sharing
the same ipc of the host.

This feature must be explicitly enabled in apiserver using the
option host-ipc-sources.

Signed-off-by: Federico Simoncelli <fsimonce@redhat.com>

pkg/capabilities/capabilities.go

@@ -41,6 +41,9 @@ type PrivilegedSources struct {
 
 	// List of pod sources for which using host pid namespace is allowed.
 	HostPIDSources []string
+
+	// List of pod sources for which using host ipc is allowed.
+	HostIPCSources []string
 }
 
 // TODO: Clean these up into a singleton
@@ -83,6 +86,7 @@ func Get() Capabilities {
 			PrivilegedSources: PrivilegedSources{
 				HostNetworkSources: []string{},
 				HostPIDSources:     []string{},
+				HostIPCSources:     []string{},
 			},
 		})
 	}