tree-wide: sort includes

Sort the includes accoding to the new coding style.

src/test/test-hashmap.c

@@ -17,8 +17,8 @@
   along with systemd; If not, see <http://www.gnu.org/licenses/>.
 ***/
 
-#include "util.h"
 #include "hashmap.h"
+#include "util.h"
 
 void test_hashmap_funcs(void);
 void test_ordered_hashmap_funcs(void);