runtime: correctly detect IPv4 forwarding

When memory cgroup is absent, there was not attempt to detect if IPv4
forwarding was enabled and therefore, docker was printing a warning
for each command spawning a new container. The test for IPv4
forwarding was guarded by the test for memory cgroup.

runtime.go

@@ -241,6 +241,7 @@ func (runtime *Runtime) UpdateCapabilities(quiet bool) {
 		if !runtime.capabilities.SwapLimit && !quiet {
 			log.Printf("WARNING: Your kernel does not support cgroup swap limit.")
 		}
+	}
 
 	content, err3 := ioutil.ReadFile("/proc/sys/net/ipv4/ip_forward")
 	runtime.capabilities.IPv4Forwarding = err3 == nil && len(content) > 0 && content[0] == '1'
@@ -248,7 +249,6 @@ func (runtime *Runtime) UpdateCapabilities(quiet bool) {
 		log.Printf("WARNING: IPv4 forwarding is disabled.")
 	}
 }
-}
 
 // FIXME: harmonize with NewGraph()
 func NewRuntime(flGraphPath string, autoRestart bool, dns []string) (*Runtime, error) {