Remove hard coding of SELinux labels on systems without proper selinux policy.

If a system is configured for SELinux but does not know about docker or
containers, then we want the transitions of the policy to work.  Hard coding
the labels causes docker to break on older Fedora and RHEL systems

Docker-DCO-1.1-Signed-off-by: Dan Walsh <dwalsh@redhat.com> (github: rhatdan)

pkg/selinux/selinux.go

@@ -313,12 +313,9 @@ func GetLxcContexts() (processLabel string, fileLabel string) {
 		return "", ""
 	}
 	lxcPath := fmt.Sprintf("%s/content/lxc_contexts", GetSELinuxPolicyRoot())
-	fileLabel = "system_u:object_r:svirt_sandbox_file_t:s0"
-	processLabel = "system_u:system_r:svirt_lxc_net_t:s0"
-
 	in, err := os.Open(lxcPath)
 	if err != nil {
-		goto exit
+		return "", ""
 	}
 	defer in.Close()
 
@@ -352,6 +349,11 @@ func GetLxcContexts() (processLabel string, fileLabel string) {
 			}
 		}
 	}
+
+	if processLabel == "" || fileLabel == "" {
+		return "", ""
+	}
+
 exit:
 	mcs := IntToMcs(os.Getpid(), 1024)
 	scon := NewContext(processLabel)