various: add missing include for namespace-util.h

Preparation for later commits for removing inclusion
of namespace-util from process-util.h

src/machine/machined-core.c

@@ -7,6 +7,7 @@
 #include "fileio.h"
 #include "iovec-util.h"
 #include "machined.h"
+#include "namespace-util.h"
 #include "process-util.h"
 #include "socket-util.h"
 #include "strv.h"

src/vmspawn/vmspawn.c

@@ -46,6 +46,7 @@
 #include "macro.h"
 #include "main-func.h"
 #include "mkdir.h"
+#include "namespace-util.h"
 #include "netif-util.h"
 #include "pager.h"
 #include "parse-argument.h"